diff --git a/ChangeLog.md b/ChangeLog.md
index 5a8f0af6..6978e6b1 100644
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -5,9 +5,53 @@ English version [by Google](https://gitflic-ru.translate.goog/project/erthink/li
 and [by Yandex](https://translated.turbopages.org/proxy_u/ru-en.en/https/gitflic.ru/project/erthink/libmdbx/blob?file=ChangeLog.md).
 
 
-## v0.12.8 (сопровождение и подготовка к релизу)
+## v0.12.9 "Ясень-4" от 2023-12-11
 
-Поддержка стабильной ветки.
+Стабилизирующий выпуск с исправлением обнаруженных ошибок и устранением недочетов.
+
+```
+git diff' stat: 32 commits, 8 files changed, 667 insertions(+), 401 deletions(-)
+Signed-off-by: Леонид Юрьев (Leonid Yuriev) <leo@yuriev.ru>
+```
+
+Исправления и доработки:
+
+ - Ликвидация зависимости от ранее удаленной опции `MDBX_ENABLE_PREFAULT`, из-за
+   чего опция `MDBX_ENABLE_MINCORE` не включалась автоматически, что приводило
+   к не-активации соответствующего улучшения и не-достижению  декларируемого уровня
+   производительности в сценариях использования в режиме `MDBX_WRITEMAP`.
+
+ - Исправление авто-установки `MDBX_ENV_CHECKPID` при отключении использования
+   функционала `madvise()` посредством опции сборки `MDBX_ENABLE_MADVISE=0`.
+   Из-за чего при поддержке системой `madvise(MADV_DONTFORK)` не включался контроль pid.
+
+ - Добавлена проверка переданного ключа на `NULL` при обработке `MDBX_GET_MULTIPLE`.
+
+ - Добавлена проверка номеров корневых страниц в `coherency_check()`.
+
+ - Обеспечен `const` для начала и конца диапазона в аргументах `mdbx_estimate_range()`.
+
+ - Из разрабатываемой версии перенесены не-нарушающие совместимости доработки C++ API:
+
+     - добавлен тип `mdbx::cursor::estimation_result`, а поведение методов
+      `cursor::estimate()` унифицировано с `cursor::move()`;
+     - для предотвращения незаметного неверного использования API, для инициализации
+       возвращаемых по ссылке срезов, вместо пустых срезов задействован `slice::invalid()`;
+     - добавлены дополнительные C++ операторы преобразования к типам C API;
+     - для совместимости со старыми стандартами C++ и старыми версиями STL перенесены
+       в public классы `buffer::move_assign_alloc` и `buffer::copy_assign_alloc`;
+     - добавлен тип `mdbx::default_buffer`;
+     - для срезов и буферов добавлены методы `hex_decode()`, `base64_decode()`, `base58_decode()`;
+     - добавлен тип `mdbx::comparator` и функций `mdbx::default_comparator()`;
+     - добавлены статические методы `buffer::hex()`, `base64()`, `base58()`;
+     - для транзакций и курсоров добавлены методы `get_/set_context`;
+     - добавлен метод `cursor::clone()`;
+
+ - Поддержка base58 приведена в соответствии с черновиком RFC.
+
+ - Переработка/исправление `to_hex()` и `from_hex()`.
+
+ - Уменьшение `MDBX_opt_rp_augment_limit` по умолчанию до 1/3 от текущего количества страниц в БД.
 
 Мелочи:
 
@@ -15,6 +59,12 @@ and [by Yandex](https://translated.turbopages.org/proxy_u/ru-en.en/https/gitflic
  - Корректировка определения `MDBX_LAST_ADDED_ERRCODE`.
  - Добавление в C++ API забытого исключения `mdbx::duplicated_lck_file`.
  - Обновление патча для старых версий buildroot.
+ - Использование в API `const MDBX_txn` где это возможно.
+ - Удаление устаревшего упоминания `MDBX_EAGAIN`.
+ - Проверка pid процесса только в функциях API требующих активной среды/env.
+ - Исправление опечаток в комментариях, в том числе  в doxygen-описании.
+ - В тестах для совместимости с проблемными версиями glibc и glibc++
+   устранено использование `std::stoull()`.
 
 
 --------------------------------------------------------------------------------
diff --git a/mdbx.h b/mdbx.h
index ece77eda..15122715 100644
--- a/mdbx.h
+++ b/mdbx.h
@@ -2119,7 +2119,8 @@ enum MDBX_option_t {
    * growth, or/and to the inability of put long values.
    *
    * The `MDBX_opt_rp_augment_limit` controls described limit for the current
-   * process. Default is 262144, it is usually enough for most cases. */
+   * process. By default this limit adjusted dynamically to 1/3 of current
+   * quantity of DB pages, which is usually enough for most cases. */
   MDBX_opt_rp_augment_limit,
 
   /** \brief Controls the in-process limit to grow a cache of dirty
@@ -2352,7 +2353,6 @@ LIBMDBX_API int mdbx_env_get_option(const MDBX_env *env,
  *                            doesn't exist.
  * \retval MDBX_EACCES        The user didn't have permission to access
  *                            the environment files.
- * \retval MDBX_EAGAIN        The environment was locked by another process.
  * \retval MDBX_BUSY          The \ref MDBX_EXCLUSIVE flag was specified and the
  *                            environment is in use by another process,
  *                            or the current process tries to open environment
@@ -4293,8 +4293,8 @@ mdbx_int64_from_key(const MDBX_val);
  * \retval MDBX_THREAD_MISMATCH  Given transaction is not owned
  *                               by current thread.
  * \retval MDBX_EINVAL   An invalid parameter was specified. */
-LIBMDBX_API int mdbx_dbi_stat(MDBX_txn *txn, MDBX_dbi dbi, MDBX_stat *stat,
-                              size_t bytes);
+LIBMDBX_API int mdbx_dbi_stat(const MDBX_txn *txn, MDBX_dbi dbi,
+                              MDBX_stat *stat, size_t bytes);
 
 /** \brief Retrieve depth (bitmask) information of nested dupsort (multi-value)
  * B+trees for given database.
@@ -4311,7 +4311,7 @@ LIBMDBX_API int mdbx_dbi_stat(MDBX_txn *txn, MDBX_dbi dbi, MDBX_stat *stat,
  *                               by current thread.
  * \retval MDBX_EINVAL       An invalid parameter was specified.
  * \retval MDBX_RESULT_TRUE  The dbi isn't a dupsort (multi-value) database. */
-LIBMDBX_API int mdbx_dbi_dupsort_depthmask(MDBX_txn *txn, MDBX_dbi dbi,
+LIBMDBX_API int mdbx_dbi_dupsort_depthmask(const MDBX_txn *txn, MDBX_dbi dbi,
                                            uint32_t *mask);
 
 /** \brief DBI state bits returted by \ref mdbx_dbi_flags_ex()
@@ -4343,13 +4343,13 @@ DEFINE_ENUM_FLAG_OPERATORS(MDBX_dbi_state_t)
  * \param [out] state  Address where the state will be returned.
  *
  * \returns A non-zero error value on failure and 0 on success. */
-LIBMDBX_API int mdbx_dbi_flags_ex(MDBX_txn *txn, MDBX_dbi dbi, unsigned *flags,
-                                  unsigned *state);
+LIBMDBX_API int mdbx_dbi_flags_ex(const MDBX_txn *txn, MDBX_dbi dbi,
+                                  unsigned *flags, unsigned *state);
 /** \brief The shortcut to calling \ref mdbx_dbi_flags_ex() with `state=NULL`
  * for discarding it result.
  * \ingroup c_statinfo */
 LIBMDBX_INLINE_API(int, mdbx_dbi_flags,
-                   (MDBX_txn * txn, MDBX_dbi dbi, unsigned *flags)) {
+                   (const MDBX_txn *txn, MDBX_dbi dbi, unsigned *flags)) {
   unsigned state;
   return mdbx_dbi_flags_ex(txn, dbi, flags, &state);
 }
@@ -4425,7 +4425,7 @@ LIBMDBX_API int mdbx_drop(MDBX_txn *txn, MDBX_dbi dbi, bool del);
  *                               by current thread.
  * \retval MDBX_NOTFOUND  The key was not in the database.
  * \retval MDBX_EINVAL    An invalid parameter was specified. */
-LIBMDBX_API int mdbx_get(MDBX_txn *txn, MDBX_dbi dbi, const MDBX_val *key,
+LIBMDBX_API int mdbx_get(const MDBX_txn *txn, MDBX_dbi dbi, const MDBX_val *key,
                          MDBX_val *data);
 
 /** \brief Get items from a database
@@ -4458,7 +4458,7 @@ LIBMDBX_API int mdbx_get(MDBX_txn *txn, MDBX_dbi dbi, const MDBX_val *key,
  *                               by current thread.
  * \retval MDBX_NOTFOUND  The key was not in the database.
  * \retval MDBX_EINVAL    An invalid parameter was specified. */
-LIBMDBX_API int mdbx_get_ex(MDBX_txn *txn, MDBX_dbi dbi, MDBX_val *key,
+LIBMDBX_API int mdbx_get_ex(const MDBX_txn *txn, MDBX_dbi dbi, MDBX_val *key,
                             MDBX_val *data, size_t *values_count);
 
 /** \brief Get equal or great item from a database.
@@ -4489,7 +4489,7 @@ LIBMDBX_API int mdbx_get_ex(MDBX_txn *txn, MDBX_dbi dbi, MDBX_val *key,
  *                               by current thread.
  * \retval MDBX_NOTFOUND      The key was not in the database.
  * \retval MDBX_EINVAL        An invalid parameter was specified. */
-LIBMDBX_API int mdbx_get_equal_or_great(MDBX_txn *txn, MDBX_dbi dbi,
+LIBMDBX_API int mdbx_get_equal_or_great(const MDBX_txn *txn, MDBX_dbi dbi,
                                         MDBX_val *key, MDBX_val *data);
 
 /** \brief Store items into a database.
@@ -4731,7 +4731,7 @@ mdbx_cursor_get_userctx(const MDBX_cursor *cursor);
  * \retval MDBX_THREAD_MISMATCH  Given transaction is not owned
  *                               by current thread.
  * \retval MDBX_EINVAL  An invalid parameter was specified. */
-LIBMDBX_API int mdbx_cursor_bind(MDBX_txn *txn, MDBX_cursor *cursor,
+LIBMDBX_API int mdbx_cursor_bind(const MDBX_txn *txn, MDBX_cursor *cursor,
                                  MDBX_dbi dbi);
 
 /** \brief Create a cursor handle for the specified transaction and DBI handle.
@@ -4764,7 +4764,7 @@ LIBMDBX_API int mdbx_cursor_bind(MDBX_txn *txn, MDBX_cursor *cursor,
  * \retval MDBX_THREAD_MISMATCH  Given transaction is not owned
  *                               by current thread.
  * \retval MDBX_EINVAL  An invalid parameter was specified. */
-LIBMDBX_API int mdbx_cursor_open(MDBX_txn *txn, MDBX_dbi dbi,
+LIBMDBX_API int mdbx_cursor_open(const MDBX_txn *txn, MDBX_dbi dbi,
                                  MDBX_cursor **cursor);
 
 /** \brief Close a cursor handle.
@@ -4807,7 +4807,7 @@ LIBMDBX_API void mdbx_cursor_close(MDBX_cursor *cursor);
  * \retval MDBX_EINVAL  An invalid parameter was specified.
  * \retval MDBX_BAD_DBI The cursor was not bound to a DBI-handle
  *                      or such a handle became invalid. */
-LIBMDBX_API int mdbx_cursor_renew(MDBX_txn *txn, MDBX_cursor *cursor);
+LIBMDBX_API int mdbx_cursor_renew(const MDBX_txn *txn, MDBX_cursor *cursor);
 
 /** \brief Return the cursor's transaction handle.
  * \ingroup c_cursors
@@ -5186,9 +5186,11 @@ LIBMDBX_API int mdbx_estimate_move(const MDBX_cursor *cursor, MDBX_val *key,
  * \param [out] distance_items  A pointer to store range estimation result.
  *
  * \returns A non-zero error value on failure and 0 on success. */
-LIBMDBX_API int mdbx_estimate_range(MDBX_txn *txn, MDBX_dbi dbi,
-                                    MDBX_val *begin_key, MDBX_val *begin_data,
-                                    MDBX_val *end_key, MDBX_val *end_data,
+LIBMDBX_API int mdbx_estimate_range(const MDBX_txn *txn, MDBX_dbi dbi,
+                                    const MDBX_val *begin_key,
+                                    const MDBX_val *begin_data,
+                                    const MDBX_val *end_key,
+                                    const MDBX_val *end_data,
                                     ptrdiff_t *distance_items);
 
 /** \brief The EPSILON value for mdbx_estimate_range()
diff --git a/mdbx.h++ b/mdbx.h++
index d4cd7077..b77d851a 100644
--- a/mdbx.h++
+++ b/mdbx.h++
@@ -362,8 +362,11 @@ using default_allocator = polymorphic_allocator;
 using default_allocator = legacy_allocator;
 #endif /* __cpp_lib_memory_resource >= 201603L */
 
-/// \brief Default singe-byte string.
-template <class ALLOCATOR = legacy_allocator>
+/// \brief Default buffer.
+using default_buffer = buffer<default_allocator, default_capacity_policy>;
+
+/// \brief Default single-byte string.
+template <class ALLOCATOR = default_allocator>
 using string = ::std::basic_string<char, ::std::char_traits<char>, ALLOCATOR>;
 
 using filehandle = ::mdbx_filehandle_t;
@@ -733,6 +736,8 @@ struct LIBMDBX_API_TYPE slice : public ::MDBX_val {
   slice &operator=(const slice &) noexcept = default;
   inline slice &operator=(slice &&src) noexcept;
   inline slice &operator=(::MDBX_val &&src);
+  operator MDBX_val *() noexcept { return this; }
+  operator const MDBX_val *() const noexcept { return this; }
 
 #if defined(DOXYGEN) ||                                                        \
     (defined(__cpp_lib_string_view) && __cpp_lib_string_view >= 201606L)
@@ -1322,8 +1327,7 @@ struct LIBMDBX_API to_base58 {
   /// \brief Returns the buffer size in bytes needed for
   /// [Base58](https://en.wikipedia.org/wiki/Base58) dump of passed slice.
   MDBX_CXX11_CONSTEXPR size_t envisage_result_length() const noexcept {
-    const size_t bytes =
-        source.length() / 8 * 11 + (source.length() % 8 * 43 + 31) / 32;
+    const size_t bytes = (source.length() * 11 + 7) / 8;
     return wrap_width ? bytes + bytes / wrap_width : bytes;
   }
 
@@ -1488,7 +1492,7 @@ struct LIBMDBX_API from_base58 {
   /// [Base58](https://en.wikipedia.org/wiki/Base58) dump from a passed slice to
   /// decoded data.
   MDBX_CXX11_CONSTEXPR size_t envisage_result_length() const noexcept {
-    return source.length() / 11 * 8 + source.length() % 11 * 32 / 43;
+    return source.length() /* могут быть все нули кодируемые один-к-одному */;
   }
 
   /// \brief Fills the destination with data decoded from
@@ -1576,10 +1580,6 @@ public:
 private:
   friend class txn;
   struct silo;
-  using move_assign_alloc =
-      allocation_aware_details::move_assign_alloc<silo, allocator_type>;
-  using copy_assign_alloc =
-      allocation_aware_details::copy_assign_alloc<silo, allocator_type>;
   using swap_alloc = allocation_aware_details::swap_alloc<silo, allocator_type>;
   struct silo /* Empty Base Class Optimization */ : public allocator_type {
     MDBX_CXX20_CONSTEXPR const allocator_type &get_allocator() const noexcept {
@@ -2071,6 +2071,11 @@ public:
   /// \todo buffer& operator>>(buffer&, ...) for reading (delegated to slice)
   /// \todo template<class X> key(X) for encoding keys while writing
 
+  using move_assign_alloc =
+      allocation_aware_details::move_assign_alloc<silo, allocator_type>;
+  using copy_assign_alloc =
+      allocation_aware_details::copy_assign_alloc<silo, allocator_type>;
+
   /// \brief Returns the associated allocator.
   MDBX_CXX20_CONSTEXPR allocator_type get_allocator() const {
     return silo_.get_allocator();
@@ -2339,6 +2344,126 @@ public:
     return slice_.as_pod<POD>();
   }
 
+  /// \brief Returns a new buffer with a hexadecimal dump of the slice content.
+  static buffer hex(const ::mdbx::slice &source, bool uppercase = false,
+                    unsigned wrap_width = 0,
+                    const allocator_type &allocator = allocator_type()) {
+    return source.template encode_hex<ALLOCATOR, CAPACITY_POLICY>(
+        uppercase, wrap_width, allocator);
+  }
+
+  /// \brief Returns a new buffer with a
+  /// [Base58](https://en.wikipedia.org/wiki/Base58) dump of the slice content.
+  static buffer base58(const ::mdbx::slice &source, unsigned wrap_width = 0,
+                       const allocator_type &allocator = allocator_type()) {
+    return source.template encode_base58<ALLOCATOR, CAPACITY_POLICY>(wrap_width,
+                                                                     allocator);
+  }
+  /// \brief Returns a new buffer with a
+  /// [Base64](https://en.wikipedia.org/wiki/Base64) dump of the slice content.
+  static buffer base64(const ::mdbx::slice &source, unsigned wrap_width = 0,
+                       const allocator_type &allocator = allocator_type()) {
+    return source.template encode_base64<ALLOCATOR, CAPACITY_POLICY>(wrap_width,
+                                                                     allocator);
+  }
+
+  /// \brief Returns a new buffer with a hexadecimal dump of the given pod.
+  template <typename POD>
+  static buffer hex(const POD &pod, bool uppercase = false,
+                    unsigned wrap_width = 0,
+                    const allocator_type &allocator = allocator_type()) {
+    return hex(mdbx::slice::wrap(pod), uppercase, wrap_width, allocator);
+  }
+
+  /// \brief Returns a new buffer with a
+  /// [Base58](https://en.wikipedia.org/wiki/Base58) dump of the given pod.
+  template <typename POD>
+  static buffer base58(const POD &pod, unsigned wrap_width = 0,
+                       const allocator_type &allocator = allocator_type()) {
+    return base58(mdbx::slice::wrap(pod), wrap_width, allocator);
+  }
+
+  /// \brief Returns a new buffer with a
+  /// [Base64](https://en.wikipedia.org/wiki/Base64) dump of the given pod.
+  template <typename POD>
+  static buffer base64(const POD &pod, unsigned wrap_width = 0,
+                       const allocator_type &allocator = allocator_type()) {
+    return base64(mdbx::slice::wrap(pod), wrap_width, allocator);
+  }
+
+  /// \brief Returns a new buffer with a hexadecimal dump of the slice content.
+  buffer encode_hex(bool uppercase = false, unsigned wrap_width = 0,
+                    const allocator_type &allocator = allocator_type()) const {
+    return slice().template encode_hex<ALLOCATOR, CAPACITY_POLICY>(
+        uppercase, wrap_width, allocator);
+  }
+
+  /// \brief Returns a new buffer with a
+  /// [Base58](https://en.wikipedia.org/wiki/Base58) dump of the slice content.
+  buffer
+  encode_base58(unsigned wrap_width = 0,
+                const allocator_type &allocator = allocator_type()) const {
+    return slice().template encode_base58<ALLOCATOR, CAPACITY_POLICY>(
+        wrap_width, allocator);
+  }
+  /// \brief Returns a new buffer with a
+  /// [Base64](https://en.wikipedia.org/wiki/Base64) dump of the slice content.
+  buffer
+  encode_base64(unsigned wrap_width = 0,
+                const allocator_type &allocator = allocator_type()) const {
+    return slice().template encode_base64<ALLOCATOR, CAPACITY_POLICY>(
+        wrap_width, allocator);
+  }
+
+  /// \brief Decodes hexadecimal dump from the slice content to returned buffer.
+  static buffer hex_decode(const ::mdbx::slice &source,
+                           bool ignore_spaces = false,
+                           const allocator_type &allocator = allocator_type()) {
+    return source.template hex_decode<ALLOCATOR, CAPACITY_POLICY>(ignore_spaces,
+                                                                  allocator);
+  }
+
+  /// \brief Decodes [Base58](https://en.wikipedia.org/wiki/Base58) dump
+  /// from the slice content to returned buffer.
+  static buffer
+  base58_decode(const ::mdbx::slice &source, bool ignore_spaces = false,
+                const allocator_type &allocator = allocator_type()) {
+    return source.template base58_decode<ALLOCATOR, CAPACITY_POLICY>(
+        ignore_spaces, allocator);
+  }
+
+  /// \brief Decodes [Base64](https://en.wikipedia.org/wiki/Base64) dump
+  /// from the slice content to returned buffer.
+  static buffer
+  base64_decode(const ::mdbx::slice &source, bool ignore_spaces = false,
+                const allocator_type &allocator = allocator_type()) {
+    return source.template base64_decode<ALLOCATOR, CAPACITY_POLICY>(
+        ignore_spaces, allocator);
+  }
+
+  /// \brief Decodes hexadecimal dump
+  /// from the buffer content to new returned buffer.
+  buffer hex_decode(bool ignore_spaces = false,
+                    const allocator_type &allocator = allocator_type()) const {
+    return hex_decode(slice(), ignore_spaces, allocator);
+  }
+
+  /// \brief Decodes [Base58](https://en.wikipedia.org/wiki/Base58) dump
+  /// from the buffer content to new returned buffer.
+  buffer
+  base58_decode(bool ignore_spaces = false,
+                const allocator_type &allocator = allocator_type()) const {
+    return base58_decode(slice(), ignore_spaces, allocator);
+  }
+
+  /// \brief Decodes [Base64](https://en.wikipedia.org/wiki/Base64) dump
+  /// from the buffer content to new returned buffer.
+  buffer
+  base64_decode(bool ignore_spaces = false,
+                const allocator_type &allocator = allocator_type()) const {
+    return base64_decode(slice(), ignore_spaces, allocator);
+  }
+
   /// \brief Reserves storage space.
   void reserve(size_t wanna_headroom, size_t wanna_tailroom) {
     wanna_headroom = ::std::min(::std::max(headroom(), wanna_headroom),
@@ -2983,6 +3108,7 @@ struct LIBMDBX_API_TYPE map_handle {
   map_handle(const map_handle &) noexcept = default;
   map_handle &operator=(const map_handle &) noexcept = default;
   operator bool() const noexcept { return dbi != 0; }
+  operator MDBX_dbi() const { return dbi; }
 
   using flags = ::MDBX_db_flags_t;
   using state = ::MDBX_dbi_state_t;
@@ -3008,6 +3134,14 @@ struct LIBMDBX_API_TYPE map_handle {
   };
 };
 
+using comparator = ::MDBX_cmp_func *;
+inline comparator default_comparator(key_mode mode) noexcept {
+  return ::mdbx_get_keycmp(static_cast<MDBX_db_flags_t>(mode));
+}
+inline comparator default_comparator(value_mode mode) noexcept {
+  return ::mdbx_get_keycmp(static_cast<MDBX_db_flags_t>(mode));
+}
+
 /// \brief Key-value pairs put mode.
 enum put_mode {
   insert_unique = MDBX_NOOVERWRITE, ///< Insert only unique keys.
@@ -3445,7 +3579,7 @@ public:
   inline void *get_context() const noexcept;
 
   /// \brief Sets the application context associated with the environment.
-  inline env &set_context(void *);
+  inline env &set_context(void *your_context);
 
   /// \brief Sets threshold to force flush the data buffers to disk, for
   /// non-sync durability modes.
@@ -3803,6 +3937,12 @@ public:
   /// \brief Return the transaction's ID.
   inline uint64_t id() const;
 
+  /// \brief Returns the application context associated with the transaction.
+  inline void *get_context() const noexcept;
+
+  /// \brief Sets the application context associated with the transaction.
+  inline txn &set_context(void *your_context);
+
   /// \brief Checks whether the given data is on a dirty page.
   inline bool is_dirty(const void *ptr) const;
 
@@ -3839,7 +3979,7 @@ public:
   txn_managed start_nested();
 
   /// \brief Opens cursor for specified key-value map handle.
-  inline cursor_managed open_cursor(map_handle map);
+  inline cursor_managed open_cursor(map_handle map) const;
 
   /// \brief Open existing key-value map.
   inline map_handle open_map(
@@ -4038,10 +4178,12 @@ public:
     put_multiple(map, key, vector.data(), vector.size(), mode);
   }
 
-  inline ptrdiff_t estimate(map_handle map, pair from, pair to) const;
-  inline ptrdiff_t estimate(map_handle map, slice from, slice to) const;
-  inline ptrdiff_t estimate_from_first(map_handle map, slice to) const;
-  inline ptrdiff_t estimate_to_last(map_handle map, slice from) const;
+  inline ptrdiff_t estimate(map_handle map, const pair &from,
+                            const pair &to) const;
+  inline ptrdiff_t estimate(map_handle map, const slice &from,
+                            const slice &to) const;
+  inline ptrdiff_t estimate_from_first(map_handle map, const slice &to) const;
+  inline ptrdiff_t estimate_to_last(map_handle map, const slice &from) const;
 };
 
 /// \brief Managed database transaction.
@@ -4122,6 +4264,7 @@ public:
   inline cursor &operator=(cursor &&other) noexcept;
   inline cursor(cursor &&other) noexcept;
   inline ~cursor() noexcept;
+  inline cursor_managed clone(void *your_context = nullptr) const;
   MDBX_CXX14_CONSTEXPR operator bool() const noexcept;
   MDBX_CXX14_CONSTEXPR operator const MDBX_cursor *() const;
   MDBX_CXX14_CONSTEXPR operator MDBX_cursor *();
@@ -4130,6 +4273,12 @@ public:
   friend MDBX_CXX11_CONSTEXPR bool operator!=(const cursor &a,
                                               const cursor &b) noexcept;
 
+  /// \brief Returns the application context associated with the cursor.
+  inline void *get_context() const noexcept;
+
+  /// \brief Sets the application context associated with the cursor.
+  inline cursor &set_context(void *your_context);
+
   enum move_operation {
     first = MDBX_FIRST,
     last = MDBX_LAST,
@@ -4154,10 +4303,13 @@ public:
 
   struct move_result : public pair_result {
     inline move_result(const cursor &cursor, bool throw_notfound);
-    inline move_result(cursor &cursor, move_operation operation,
-                       bool throw_notfound);
-    inline move_result(cursor &cursor, move_operation operation,
-                       const slice &key, bool throw_notfound);
+    move_result(cursor &cursor, move_operation operation, bool throw_notfound)
+        : move_result(cursor, operation, slice::invalid(), slice::invalid(),
+                      throw_notfound) {}
+    move_result(cursor &cursor, move_operation operation, const slice &key,
+                bool throw_notfound)
+        : move_result(cursor, operation, key, slice::invalid(),
+                      throw_notfound) {}
     inline move_result(cursor &cursor, move_operation operation,
                        const slice &key, const slice &value,
                        bool throw_notfound);
@@ -4165,6 +4317,20 @@ public:
     move_result &operator=(const move_result &) noexcept = default;
   };
 
+  struct estimate_result : public pair {
+    ptrdiff_t approximate_quantity;
+    estimate_result(const cursor &cursor, move_operation operation)
+        : estimate_result(cursor, operation, slice::invalid(),
+                          slice::invalid()) {}
+    estimate_result(const cursor &cursor, move_operation operation,
+                    const slice &key)
+        : estimate_result(cursor, operation, key, slice::invalid()) {}
+    inline estimate_result(const cursor &cursor, move_operation operation,
+                           const slice &key, const slice &value);
+    estimate_result(const estimate_result &) noexcept = default;
+    estimate_result &operator=(const estimate_result &) noexcept = default;
+  };
+
 protected:
   inline bool move(move_operation operation, MDBX_val *key, MDBX_val *value,
                    bool throw_notfound) const
@@ -4209,19 +4375,20 @@ public:
   inline bool eof() const;
   inline bool on_first() const;
   inline bool on_last() const;
-  inline ptrdiff_t estimate(slice key, slice value) const;
-  inline ptrdiff_t estimate(slice key) const;
-  inline ptrdiff_t estimate(move_operation operation) const;
+  inline estimate_result estimate(const slice &key, const slice &value) const;
+  inline estimate_result estimate(const slice &key) const;
+  inline estimate_result estimate(move_operation operation) const;
+  inline estimate_result estimate(move_operation operation, slice &key) const;
 
   //----------------------------------------------------------------------------
 
   /// \brief Renew/bind a cursor with a new transaction and previously used
   /// key-value map handle.
-  inline void renew(::mdbx::txn &txn);
+  inline void renew(const ::mdbx::txn &txn);
 
   /// \brief Bind/renew a cursor with a new transaction and specified key-value
   /// map handle.
-  inline void bind(::mdbx::txn &txn, ::mdbx::map_handle map_handle);
+  inline void bind(const ::mdbx::txn &txn, ::mdbx::map_handle map_handle);
 
   /// \brief Returns the cursor's transaction.
   inline ::mdbx::txn txn() const;
@@ -4275,7 +4442,8 @@ class LIBMDBX_API_TYPE cursor_managed : public cursor {
 
 public:
   /// \brief Creates a new managed cursor with underlying object.
-  cursor_managed() : cursor_managed(::mdbx_cursor_create(nullptr)) {
+  cursor_managed(void *your_context = nullptr)
+      : cursor_managed(::mdbx_cursor_create(your_context)) {
     if (MDBX_UNLIKELY(!handle_))
       MDBX_CXX20_UNLIKELY error::throw_exception(MDBX_ENOMEM);
   }
@@ -5417,6 +5585,15 @@ MDBX_CXX11_CONSTEXPR bool operator!=(const txn &a, const txn &b) noexcept {
   return a.handle_ != b.handle_;
 }
 
+inline void *txn::get_context() const noexcept {
+  return mdbx_txn_get_userctx(handle_);
+}
+
+inline txn &txn::set_context(void *ptr) {
+  error::success_or_throw(::mdbx_txn_set_userctx(handle_, ptr));
+  return *this;
+}
+
 inline bool txn::is_dirty(const void *ptr) const {
   int err = ::mdbx_is_dirty(handle_, ptr);
   switch (err) {
@@ -5457,7 +5634,7 @@ inline txn::info txn::get_info(bool scan_reader_lock_table) const {
   return r;
 }
 
-inline cursor_managed txn::open_cursor(map_handle map) {
+inline cursor_managed txn::open_cursor(map_handle map) const {
   MDBX_cursor *ptr;
   error::success_or_throw(::mdbx_cursor_open(handle_, map.dbi, &ptr));
   return cursor_managed(ptr);
@@ -5855,28 +6032,32 @@ inline size_t txn::put_multiple(map_handle map, const slice &key,
   return args[1].iov_len /* done item count */;
 }
 
-inline ptrdiff_t txn::estimate(map_handle map, pair from, pair to) const {
+inline ptrdiff_t txn::estimate(map_handle map, const pair &from,
+                               const pair &to) const {
   ptrdiff_t result;
   error::success_or_throw(mdbx_estimate_range(
       handle_, map.dbi, &from.key, &from.value, &to.key, &to.value, &result));
   return result;
 }
 
-inline ptrdiff_t txn::estimate(map_handle map, slice from, slice to) const {
+inline ptrdiff_t txn::estimate(map_handle map, const slice &from,
+                               const slice &to) const {
   ptrdiff_t result;
   error::success_or_throw(mdbx_estimate_range(handle_, map.dbi, &from, nullptr,
                                               &to, nullptr, &result));
   return result;
 }
 
-inline ptrdiff_t txn::estimate_from_first(map_handle map, slice to) const {
+inline ptrdiff_t txn::estimate_from_first(map_handle map,
+                                          const slice &to) const {
   ptrdiff_t result;
   error::success_or_throw(mdbx_estimate_range(handle_, map.dbi, nullptr,
                                               nullptr, &to, nullptr, &result));
   return result;
 }
 
-inline ptrdiff_t txn::estimate_to_last(map_handle map, slice from) const {
+inline ptrdiff_t txn::estimate_to_last(map_handle map,
+                                       const slice &from) const {
   ptrdiff_t result;
   error::success_or_throw(mdbx_estimate_range(handle_, map.dbi, &from, nullptr,
                                               nullptr, nullptr, &result));
@@ -5887,6 +6068,21 @@ inline ptrdiff_t txn::estimate_to_last(map_handle map, slice from) const {
 
 MDBX_CXX11_CONSTEXPR cursor::cursor(MDBX_cursor *ptr) noexcept : handle_(ptr) {}
 
+inline cursor_managed cursor::clone(void *your_context) const {
+  cursor_managed clone(your_context);
+  error::success_or_throw(::mdbx_cursor_copy(handle_, clone.handle_));
+  return clone;
+}
+
+inline void *cursor::get_context() const noexcept {
+  return mdbx_cursor_get_userctx(handle_);
+}
+
+inline cursor &cursor::set_context(void *ptr) {
+  error::success_or_throw(::mdbx_cursor_set_userctx(handle_, ptr));
+  return *this;
+}
+
 inline cursor &cursor::operator=(cursor &&other) noexcept {
   handle_ = other.handle_;
   other.handle_ = nullptr;
@@ -5925,22 +6121,8 @@ MDBX_CXX11_CONSTEXPR bool operator!=(const cursor &a,
 
 inline cursor::move_result::move_result(const cursor &cursor,
                                         bool throw_notfound)
-    : pair_result(key, value, false) {
-  done = cursor.move(get_current, &key, &value, throw_notfound);
-}
-
-inline cursor::move_result::move_result(cursor &cursor,
-                                        move_operation operation,
-                                        bool throw_notfound)
-    : pair_result(key, value, false) {
-  done = cursor.move(operation, &key, &value, throw_notfound);
-}
-
-inline cursor::move_result::move_result(cursor &cursor,
-                                        move_operation operation,
-                                        const slice &key, bool throw_notfound)
-    : pair_result(key, slice(), false) {
-  this->done = cursor.move(operation, &this->key, &this->value, throw_notfound);
+    : pair_result(slice(), slice(), false) {
+  done = cursor.move(get_current, &this->key, &this->value, throw_notfound);
 }
 
 inline cursor::move_result::move_result(cursor &cursor,
@@ -5967,6 +6149,14 @@ inline bool cursor::move(move_operation operation, MDBX_val *key,
   }
 }
 
+inline cursor::estimate_result::estimate_result(const cursor &cursor,
+                                                move_operation operation,
+                                                const slice &key,
+                                                const slice &value)
+    : pair(key, value), approximate_quantity(PTRDIFF_MIN) {
+  approximate_quantity = cursor.estimate(operation, &this->key, &this->value);
+}
+
 inline ptrdiff_t cursor::estimate(move_operation operation, MDBX_val *key,
                                   MDBX_val *value) const {
   ptrdiff_t result;
@@ -6089,24 +6279,26 @@ inline bool cursor::on_last() const {
   return error::boolean_or_throw(::mdbx_cursor_on_last(*this));
 }
 
-inline ptrdiff_t cursor::estimate(slice key, slice value) const {
-  return estimate(multi_exactkey_lowerboundvalue, &key, &value);
+inline cursor::estimate_result cursor::estimate(const slice &key,
+                                                const slice &value) const {
+  return estimate_result(*this, multi_exactkey_lowerboundvalue, key, value);
 }
 
-inline ptrdiff_t cursor::estimate(slice key) const {
-  return estimate(key_lowerbound, &key, nullptr);
+inline cursor::estimate_result cursor::estimate(const slice &key) const {
+  return estimate_result(*this, key_lowerbound, key);
 }
 
-inline ptrdiff_t cursor::estimate(move_operation operation) const {
-  slice unused_key;
-  return estimate(operation, &unused_key, nullptr);
+inline cursor::estimate_result
+cursor::estimate(move_operation operation) const {
+  return estimate_result(*this, operation);
 }
 
-inline void cursor::renew(::mdbx::txn &txn) {
+inline void cursor::renew(const ::mdbx::txn &txn) {
   error::success_or_throw(::mdbx_cursor_renew(txn, handle_));
 }
 
-inline void cursor::bind(::mdbx::txn &txn, ::mdbx::map_handle map_handle) {
+inline void cursor::bind(const ::mdbx::txn &txn,
+                         ::mdbx::map_handle map_handle) {
   error::success_or_throw(::mdbx_cursor_bind(txn, handle_, map_handle.dbi));
 }
 
diff --git a/src/core.c b/src/core.c
index 899b65af..9d142343 100644
--- a/src/core.c
+++ b/src/core.c
@@ -3386,7 +3386,7 @@ static int __must_check_result cursor_first(MDBX_cursor *mc, MDBX_val *key,
 static int __must_check_result cursor_last(MDBX_cursor *mc, MDBX_val *key,
                                            MDBX_val *data);
 
-static int __must_check_result cursor_init(MDBX_cursor *mc, MDBX_txn *txn,
+static int __must_check_result cursor_init(MDBX_cursor *mc, const MDBX_txn *txn,
                                            size_t dbi);
 static int __must_check_result cursor_xinit0(MDBX_cursor *mc);
 static int __must_check_result cursor_xinit1(MDBX_cursor *mc, MDBX_node *node,
@@ -5979,8 +5979,8 @@ __cold static void munlock_all(const MDBX_env *env) {
 }
 
 __cold static unsigned default_rp_augment_limit(const MDBX_env *env) {
-  /* default rp_augment_limit = ceil(npages / gold_ratio) */
-  const size_t augment = (env->me_dbgeo.now >> (env->me_psize2log + 10)) * 633u;
+  /* default rp_augment_limit = npages / 3 */
+  const size_t augment = env->me_dbgeo.now / 3 >> env->me_psize2log;
   eASSERT(env, augment < MDBX_PGL_LIMIT);
   return pnl_bytes2size(pnl_size2bytes(
       (augment > MDBX_PNL_INITIAL) ? augment : MDBX_PNL_INITIAL));
@@ -7315,7 +7315,7 @@ static pgr_t page_alloc_slowpath(const MDBX_cursor *const mc, const size_t num,
      * простейших случаях (тривиальный бенчмарк) интегральная производительность
      * становится вдвое меньше. А на платформах без mincore() и с проблемной
      * подсистемой виртуальной памяти ситуация может быть многократно хуже.
-     * Поэтому избегаем затрат в ситуациях когда prefaukt-write скорее всего не
+     * Поэтому избегаем затрат в ситуациях когда prefault-write скорее всего не
      * нужна. */
     const bool readahead_enabled = env->me_lck->mti_readahead_anchor & 1;
     const pgno_t readahead_edge = env->me_lck->mti_readahead_anchor >> 1;
@@ -8258,17 +8258,16 @@ static __inline int check_env(const MDBX_env *env, const bool wanna_active) {
   if (unlikely(env->me_signature.weak != MDBX_ME_SIGNATURE))
     return MDBX_EBADSIGN;
 
-#if MDBX_ENV_CHECKPID
-  if (unlikely(env->me_pid != osal_getpid())) {
-    ((MDBX_env *)env)->me_flags |= MDBX_FATAL_ERROR;
-    return MDBX_PANIC;
-  }
-#endif /* MDBX_ENV_CHECKPID */
-
   if (unlikely(env->me_flags & MDBX_FATAL_ERROR))
     return MDBX_PANIC;
 
   if (wanna_active) {
+#if MDBX_ENV_CHECKPID
+    if (unlikely(env->me_pid != osal_getpid())) {
+      ((MDBX_env *)env)->me_flags |= MDBX_FATAL_ERROR;
+      return MDBX_PANIC;
+    }
+#endif /* MDBX_ENV_CHECKPID */
     if (unlikely((env->me_flags & MDBX_ENV_ACTIVE) == 0))
       return MDBX_EPERM;
     eASSERT(env, env->me_map != nullptr);
@@ -8615,20 +8614,45 @@ static bool coherency_check(const MDBX_env *env, const txnid_t txnid,
                             const volatile MDBX_meta *meta, bool report) {
   const txnid_t freedb_mod_txnid = dbs[FREE_DBI].md_mod_txnid;
   const txnid_t maindb_mod_txnid = dbs[MAIN_DBI].md_mod_txnid;
+  const pgno_t last_pgno = meta->mm_geo.now;
 
   const pgno_t freedb_root_pgno = dbs[FREE_DBI].md_root;
-  const MDBX_page *freedb_root = (env->me_map && freedb_root_pgno != P_INVALID)
+  const MDBX_page *freedb_root = (env->me_map && freedb_root_pgno < last_pgno)
                                      ? pgno2page(env, freedb_root_pgno)
                                      : nullptr;
 
   const pgno_t maindb_root_pgno = dbs[MAIN_DBI].md_root;
-  const MDBX_page *maindb_root = (env->me_map && maindb_root_pgno != P_INVALID)
+  const MDBX_page *maindb_root = (env->me_map && maindb_root_pgno < last_pgno)
                                      ? pgno2page(env, maindb_root_pgno)
                                      : nullptr;
   const uint64_t magic_and_version =
       unaligned_peek_u64_volatile(4, &meta->mm_magic_and_version);
 
   bool ok = true;
+  if (freedb_root_pgno != P_INVALID &&
+      unlikely(freedb_root_pgno >= last_pgno)) {
+    if (report)
+      WARNING(
+          "catch invalid %sdb root %" PRIaPGNO " for meta_txnid %" PRIaTXN
+          " %s",
+          "free", freedb_root_pgno, txnid,
+          (env->me_stuck_meta < 0)
+              ? "(workaround for incoherent flaw of unified page/buffer cache)"
+              : "(wagering meta)");
+    ok = false;
+  }
+  if (maindb_root_pgno != P_INVALID &&
+      unlikely(maindb_root_pgno >= last_pgno)) {
+    if (report)
+      WARNING(
+          "catch invalid %sdb root %" PRIaPGNO " for meta_txnid %" PRIaTXN
+          " %s",
+          "main", maindb_root_pgno, txnid,
+          (env->me_stuck_meta < 0)
+              ? "(workaround for incoherent flaw of unified page/buffer cache)"
+              : "(wagering meta)");
+    ok = false;
+  }
   if (unlikely(txnid < freedb_mod_txnid ||
                (!freedb_mod_txnid && freedb_root &&
                 likely(magic_and_version == MDBX_DATA_MAGIC)))) {
@@ -9579,7 +9603,7 @@ int mdbx_txn_flags(const MDBX_txn *txn) {
 }
 
 /* Check for misused dbi handles */
-static __inline bool dbi_changed(MDBX_txn *txn, size_t dbi) {
+static __inline bool dbi_changed(const MDBX_txn *txn, size_t dbi) {
   if (txn->mt_dbiseqs == txn->mt_env->me_dbiseqs)
     return false;
   if (likely(
@@ -11170,7 +11194,7 @@ static int txn_write(MDBX_txn *txn, iov_ctx_t *ctx) {
 }
 
 /* Check txn and dbi arguments to a function */
-static __always_inline bool check_dbi(MDBX_txn *txn, MDBX_dbi dbi,
+static __always_inline bool check_dbi(const MDBX_txn *txn, MDBX_dbi dbi,
                                       unsigned validity) {
   if (likely(dbi < txn->mt_numdbs)) {
     if (likely(!dbi_changed(txn, dbi))) {
@@ -11181,7 +11205,7 @@ static __always_inline bool check_dbi(MDBX_txn *txn, MDBX_dbi dbi,
         return false;
     }
   }
-  return dbi_import(txn, dbi);
+  return dbi_import((MDBX_txn *)txn, dbi);
 }
 
 /* Merge child txn into parent */
@@ -16078,7 +16102,8 @@ static __always_inline int node_read(MDBX_cursor *mc, const MDBX_node *node,
   return node_read_bigdata(mc, node, data, mp);
 }
 
-int mdbx_get(MDBX_txn *txn, MDBX_dbi dbi, const MDBX_val *key, MDBX_val *data) {
+int mdbx_get(const MDBX_txn *txn, MDBX_dbi dbi, const MDBX_val *key,
+             MDBX_val *data) {
   DKBUF_DEBUG;
   DEBUG("===> get db %u key [%s]", dbi, DKEY_DEBUG(key));
 
@@ -16100,7 +16125,7 @@ int mdbx_get(MDBX_txn *txn, MDBX_dbi dbi, const MDBX_val *key, MDBX_val *data) {
   return cursor_set(&cx.outer, (MDBX_val *)key, data, MDBX_SET).err;
 }
 
-int mdbx_get_equal_or_great(MDBX_txn *txn, MDBX_dbi dbi, MDBX_val *key,
+int mdbx_get_equal_or_great(const MDBX_txn *txn, MDBX_dbi dbi, MDBX_val *key,
                             MDBX_val *data) {
   int rc = check_txn(txn, MDBX_TXN_BLOCKED);
   if (unlikely(rc != MDBX_SUCCESS))
@@ -16123,8 +16148,8 @@ int mdbx_get_equal_or_great(MDBX_txn *txn, MDBX_dbi dbi, MDBX_val *key,
   return cursor_get(&cx.outer, key, data, MDBX_SET_LOWERBOUND);
 }
 
-int mdbx_get_ex(MDBX_txn *txn, MDBX_dbi dbi, MDBX_val *key, MDBX_val *data,
-                size_t *values_count) {
+int mdbx_get_ex(const MDBX_txn *txn, MDBX_dbi dbi, MDBX_val *key,
+                MDBX_val *data, size_t *values_count) {
   DKBUF_DEBUG;
   DEBUG("===> get db %u key [%s]", dbi, DKEY_DEBUG(key));
 
@@ -16883,24 +16908,30 @@ static __hot int cursor_get(MDBX_cursor *mc, MDBX_val *key, MDBX_val *data,
       return MDBX_EINVAL;
     if (unlikely((mc->mc_db->md_flags & MDBX_DUPFIXED) == 0))
       return MDBX_INCOMPATIBLE;
-    rc = (mc->mc_flags & C_INITIALIZED)
-             ? MDBX_SUCCESS
-             : cursor_set(mc, key, data, MDBX_SET).err;
-    if ((mc->mc_xcursor->mx_cursor.mc_flags & (C_INITIALIZED | C_EOF)) !=
-        C_INITIALIZED)
+    if ((mc->mc_flags & C_INITIALIZED) == 0) {
+      if (unlikely(!key))
+        return MDBX_EINVAL;
+      rc = cursor_set(mc, key, data, MDBX_SET).err;
+      if (unlikely(rc != MDBX_SUCCESS))
+        break;
+    }
+    rc = MDBX_SUCCESS;
+    if (unlikely(C_INITIALIZED != (mc->mc_xcursor->mx_cursor.mc_flags &
+                                   (C_INITIALIZED | C_EOF)))) {
+      rc = MDBX_NOTFOUND;
       break;
-    goto fetchm;
+    }
+    goto fetch_multiple;
   case MDBX_NEXT_MULTIPLE:
-    if (unlikely(data == NULL))
+    if (unlikely(!data))
       return MDBX_EINVAL;
     if (unlikely(!(mc->mc_db->md_flags & MDBX_DUPFIXED)))
       return MDBX_INCOMPATIBLE;
     rc = cursor_next(mc, key, data, MDBX_NEXT_DUP);
     if (rc == MDBX_SUCCESS) {
       if (mc->mc_xcursor->mx_cursor.mc_flags & C_INITIALIZED) {
-        MDBX_cursor *mx;
-      fetchm:
-        mx = &mc->mc_xcursor->mx_cursor;
+      fetch_multiple:;
+        MDBX_cursor *mx = &mc->mc_xcursor->mx_cursor;
         data->iov_len =
             page_numkeys(mx->mc_pg[mx->mc_top]) * mx->mc_db->md_xsize;
         data->iov_base = page_data(mx->mc_pg[mx->mc_top]);
@@ -16911,21 +16942,20 @@ static __hot int cursor_get(MDBX_cursor *mc, MDBX_val *key, MDBX_val *data,
     }
     break;
   case MDBX_PREV_MULTIPLE:
-    if (data == NULL)
+    if (unlikely(!data))
       return MDBX_EINVAL;
     if (!(mc->mc_db->md_flags & MDBX_DUPFIXED))
       return MDBX_INCOMPATIBLE;
     rc = MDBX_SUCCESS;
-    if (!(mc->mc_flags & C_INITIALIZED))
+    if ((mc->mc_flags & C_INITIALIZED) == 0)
       rc = cursor_last(mc, key, data);
     if (rc == MDBX_SUCCESS) {
       MDBX_cursor *mx = &mc->mc_xcursor->mx_cursor;
+      rc = MDBX_NOTFOUND;
       if (mx->mc_flags & C_INITIALIZED) {
         rc = cursor_sibling(mx, SIBLING_LEFT);
         if (rc == MDBX_SUCCESS)
-          goto fetchm;
-      } else {
-        rc = MDBX_NOTFOUND;
+          goto fetch_multiple;
       }
     }
     break;
@@ -18754,13 +18784,13 @@ static int cursor_xinit2(MDBX_cursor *mc, MDBX_xcursor *src_mx,
 }
 
 static __inline int couple_init(MDBX_cursor_couple *couple, const size_t dbi,
-                                MDBX_txn *const txn, MDBX_db *const db,
+                                const MDBX_txn *const txn, MDBX_db *const db,
                                 MDBX_dbx *const dbx, uint8_t *const dbstate) {
   couple->outer.mc_signature = MDBX_MC_LIVE;
   couple->outer.mc_next = NULL;
   couple->outer.mc_backup = NULL;
   couple->outer.mc_dbi = (MDBX_dbi)dbi;
-  couple->outer.mc_txn = txn;
+  couple->outer.mc_txn = (MDBX_txn *)txn;
   couple->outer.mc_db = db;
   couple->outer.mc_dbx = dbx;
   couple->outer.mc_dbistate = dbstate;
@@ -18798,7 +18828,7 @@ static __inline int couple_init(MDBX_cursor_couple *couple, const size_t dbi,
 }
 
 /* Initialize a cursor for a given transaction and database. */
-static int cursor_init(MDBX_cursor *mc, MDBX_txn *txn, size_t dbi) {
+static int cursor_init(MDBX_cursor *mc, const MDBX_txn *txn, size_t dbi) {
   STATIC_ASSERT(offsetof(MDBX_cursor_couple, outer) == 0);
   return couple_init(container_of(mc, MDBX_cursor_couple, outer), dbi, txn,
                      &txn->mt_dbs[dbi], &txn->mt_dbxs[dbi],
@@ -18841,7 +18871,7 @@ void *mdbx_cursor_get_userctx(const MDBX_cursor *mc) {
   return couple->mc_userctx;
 }
 
-int mdbx_cursor_bind(MDBX_txn *txn, MDBX_cursor *mc, MDBX_dbi dbi) {
+int mdbx_cursor_bind(const MDBX_txn *txn, MDBX_cursor *mc, MDBX_dbi dbi) {
   if (unlikely(!mc))
     return MDBX_EINVAL;
 
@@ -18913,7 +18943,7 @@ int mdbx_cursor_bind(MDBX_txn *txn, MDBX_cursor *mc, MDBX_dbi dbi) {
   return MDBX_SUCCESS;
 }
 
-int mdbx_cursor_open(MDBX_txn *txn, MDBX_dbi dbi, MDBX_cursor **ret) {
+int mdbx_cursor_open(const MDBX_txn *txn, MDBX_dbi dbi, MDBX_cursor **ret) {
   if (unlikely(!ret))
     return MDBX_EINVAL;
   *ret = NULL;
@@ -18932,7 +18962,7 @@ int mdbx_cursor_open(MDBX_txn *txn, MDBX_dbi dbi, MDBX_cursor **ret) {
   return MDBX_SUCCESS;
 }
 
-int mdbx_cursor_renew(MDBX_txn *txn, MDBX_cursor *mc) {
+int mdbx_cursor_renew(const MDBX_txn *txn, MDBX_cursor *mc) {
   return likely(mc) ? mdbx_cursor_bind(txn, mc, mc->mc_dbi) : MDBX_EINVAL;
 }
 
@@ -22199,7 +22229,7 @@ __cold int mdbx_env_stat_ex(const MDBX_env *env, const MDBX_txn *txn,
   return rc;
 }
 
-__cold int mdbx_dbi_dupsort_depthmask(MDBX_txn *txn, MDBX_dbi dbi,
+__cold int mdbx_dbi_dupsort_depthmask(const MDBX_txn *txn, MDBX_dbi dbi,
                                       uint32_t *mask) {
   int rc = check_txn(txn, MDBX_TXN_BLOCKED);
   if (unlikely(rc != MDBX_SUCCESS))
@@ -22817,7 +22847,7 @@ int mdbx_dbi_open_ex2(MDBX_txn *txn, const MDBX_val *name,
   return dbi_open(txn, name, flags, dbi, keycmp, datacmp);
 }
 
-__cold int mdbx_dbi_stat(MDBX_txn *txn, MDBX_dbi dbi, MDBX_stat *dest,
+__cold int mdbx_dbi_stat(const MDBX_txn *txn, MDBX_dbi dbi, MDBX_stat *dest,
                          size_t bytes) {
   int rc = check_txn(txn, MDBX_TXN_BLOCKED);
   if (unlikely(rc != MDBX_SUCCESS))
@@ -22837,7 +22867,7 @@ __cold int mdbx_dbi_stat(MDBX_txn *txn, MDBX_dbi dbi, MDBX_stat *dest,
     return MDBX_BAD_TXN;
 
   if (unlikely(txn->mt_dbistate[dbi] & DBI_STALE)) {
-    rc = fetch_sdb(txn, dbi);
+    rc = fetch_sdb((MDBX_txn *)txn, dbi);
     if (unlikely(rc != MDBX_SUCCESS))
       return rc;
   }
@@ -22898,7 +22928,7 @@ int mdbx_dbi_close(MDBX_env *env, MDBX_dbi dbi) {
   return rc;
 }
 
-int mdbx_dbi_flags_ex(MDBX_txn *txn, MDBX_dbi dbi, unsigned *flags,
+int mdbx_dbi_flags_ex(const MDBX_txn *txn, MDBX_dbi dbi, unsigned *flags,
                       unsigned *state) {
   int rc = check_txn(txn, MDBX_TXN_BLOCKED - MDBX_TXN_ERROR);
   if (unlikely(rc != MDBX_SUCCESS))
@@ -24069,9 +24099,10 @@ int mdbx_estimate_move(const MDBX_cursor *cursor, MDBX_val *key, MDBX_val *data,
   return mdbx_estimate_distance(cursor, &next.outer, distance_items);
 }
 
-int mdbx_estimate_range(MDBX_txn *txn, MDBX_dbi dbi, MDBX_val *begin_key,
-                        MDBX_val *begin_data, MDBX_val *end_key,
-                        MDBX_val *end_data, ptrdiff_t *size_items) {
+int mdbx_estimate_range(const MDBX_txn *txn, MDBX_dbi dbi,
+                        const MDBX_val *begin_key, const MDBX_val *begin_data,
+                        const MDBX_val *end_key, const MDBX_val *end_data,
+                        ptrdiff_t *size_items) {
   int rc = check_txn(txn, MDBX_TXN_BLOCKED);
   if (unlikely(rc != MDBX_SUCCESS))
     return rc;
@@ -24102,13 +24133,13 @@ int mdbx_estimate_range(MDBX_txn *txn, MDBX_dbi dbi, MDBX_val *begin_key,
     return MDBX_SUCCESS;
   }
 
+  MDBX_val stub;
   if (!begin_key) {
     if (unlikely(!end_key)) {
       /* LY: FIRST..LAST case */
       *size_items = (ptrdiff_t)begin.outer.mc_db->md_entries;
       return MDBX_SUCCESS;
     }
-    MDBX_val stub = {0, 0};
     rc = cursor_first(&begin.outer, &stub, &stub);
     if (unlikely(end_key == MDBX_EPSILON)) {
       /* LY: FIRST..+epsilon case */
@@ -24120,7 +24151,6 @@ int mdbx_estimate_range(MDBX_txn *txn, MDBX_dbi dbi, MDBX_val *begin_key,
     if (unlikely(begin_key == MDBX_EPSILON)) {
       if (end_key == NULL) {
         /* LY: -epsilon..LAST case */
-        MDBX_val stub = {0, 0};
         rc = cursor_last(&begin.outer, &stub, &stub);
         return (rc == MDBX_SUCCESS)
                    ? mdbx_cursor_count(&begin.outer, (size_t *)size_items)
@@ -24138,7 +24168,7 @@ int mdbx_estimate_range(MDBX_txn *txn, MDBX_dbi dbi, MDBX_val *begin_key,
         (begin_key == end_key ||
          begin.outer.mc_dbx->md_cmp(begin_key, end_key) == 0)) {
       /* LY: single key case */
-      rc = cursor_set(&begin.outer, begin_key, NULL, MDBX_SET).err;
+      rc = cursor_set(&begin.outer, (MDBX_val *)begin_key, NULL, MDBX_SET).err;
       if (unlikely(rc != MDBX_SUCCESS)) {
         *size_items = 0;
         return (rc == MDBX_NOTFOUND) ? MDBX_SUCCESS : rc;
@@ -24159,10 +24189,14 @@ int mdbx_estimate_range(MDBX_txn *txn, MDBX_dbi dbi, MDBX_val *begin_key,
         }
       }
       return MDBX_SUCCESS;
-    } else {
-      rc = cursor_set(&begin.outer, begin_key, begin_data,
-                      begin_data ? MDBX_GET_BOTH_RANGE : MDBX_SET_RANGE)
+    } else if (begin_data) {
+      stub = *begin_data;
+      rc = cursor_set(&begin.outer, (MDBX_val *)begin_key, &stub,
+                      MDBX_GET_BOTH_RANGE)
                .err;
+    } else {
+      stub = *begin_key;
+      rc = cursor_set(&begin.outer, &stub, nullptr, MDBX_SET_RANGE).err;
     }
   }
 
@@ -24175,13 +24209,15 @@ int mdbx_estimate_range(MDBX_txn *txn, MDBX_dbi dbi, MDBX_val *begin_key,
   rc = cursor_init(&end.outer, txn, dbi);
   if (unlikely(rc != MDBX_SUCCESS))
     return rc;
-  if (!end_key) {
-    MDBX_val stub = {0, 0};
+  if (!end_key)
     rc = cursor_last(&end.outer, &stub, &stub);
-  } else {
-    rc = cursor_set(&end.outer, end_key, end_data,
-                    end_data ? MDBX_GET_BOTH_RANGE : MDBX_SET_RANGE)
+  else if (end_data) {
+    stub = *end_data;
+    rc = cursor_set(&end.outer, (MDBX_val *)end_key, &stub, MDBX_GET_BOTH_RANGE)
              .err;
+  } else {
+    stub = *end_key;
+    rc = cursor_set(&end.outer, &stub, nullptr, MDBX_SET_RANGE).err;
   }
   if (unlikely(rc != MDBX_SUCCESS)) {
     if (rc != MDBX_NOTFOUND || !(end.outer.mc_flags & C_INITIALIZED))
@@ -25411,7 +25447,8 @@ LIBMDBX_API __cold int mdbx_env_info(const MDBX_env *env, MDBX_envinfo *info,
   return __inline_mdbx_env_info(env, info, bytes);
 }
 
-LIBMDBX_API int mdbx_dbi_flags(MDBX_txn *txn, MDBX_dbi dbi, unsigned *flags) {
+LIBMDBX_API int mdbx_dbi_flags(const MDBX_txn *txn, MDBX_dbi dbi,
+                               unsigned *flags) {
   return __inline_mdbx_dbi_flags(txn, dbi, flags);
 }
 
diff --git a/src/mdbx.c++ b/src/mdbx.c++
index 9ac6cd71..31c1e6a8 100644
--- a/src/mdbx.c++
+++ b/src/mdbx.c++
@@ -207,6 +207,44 @@ __cold  bug::~bug() noexcept {}
 
 #endif /* Unused*/
 
+struct line_wrapper {
+  char *line, *ptr;
+  line_wrapper(char *buf) noexcept : line(buf), ptr(buf) {}
+  void put(char c, size_t wrap_width) noexcept {
+    *ptr++ = c;
+    if (wrap_width && ptr >= wrap_width + line) {
+      *ptr++ = '\n';
+      line = ptr;
+    }
+  }
+  void put(const ::mdbx::slice &chunk, size_t wrap_width) noexcept {
+    if (!wrap_width || wrap_width > (ptr - line) + chunk.length()) {
+      memcpy(ptr, chunk.data(), chunk.length());
+      ptr += chunk.length();
+    } else {
+      for (size_t i = 0; i < chunk.length(); ++i)
+        put(chunk.char_ptr()[i], wrap_width);
+    }
+  }
+};
+
+template <typename TYPE, unsigned INPLACE_BYTES = unsigned(sizeof(void *) * 64)>
+struct temp_buffer {
+  TYPE inplace[(INPLACE_BYTES + sizeof(TYPE) - 1) / sizeof(TYPE)];
+  const size_t size;
+  TYPE *const area;
+  temp_buffer(size_t bytes)
+      : size((bytes + sizeof(TYPE) - 1) / sizeof(TYPE)),
+        area((bytes > sizeof(inplace)) ? new TYPE[size] : inplace) {
+    memset(area, 0, sizeof(TYPE) * size);
+  }
+  ~temp_buffer() {
+    if (area != inplace)
+      delete[] area;
+  }
+  TYPE *end() const { return area + size; }
+};
+
 } // namespace
 
 //------------------------------------------------------------------------------
@@ -599,7 +637,7 @@ char *to_hex::write_bytes(char *__restrict const dest, size_t dest_size) const {
 
   auto ptr = dest;
   auto src = source.byte_ptr();
-  const char alphabase = (uppercase ? 'A' : 'a') - 10;
+  const char alpha_shift = (uppercase ? 'A' : 'a') - '9' - 1;
   auto line = ptr;
   for (const auto end = source.end_byte_ptr(); src != end; ++src) {
     if (wrap_width && size_t(ptr - line) >= wrap_width) {
@@ -608,8 +646,8 @@ char *to_hex::write_bytes(char *__restrict const dest, size_t dest_size) const {
     }
     const int8_t hi = *src >> 4;
     const int8_t lo = *src & 15;
-    ptr[0] = char(alphabase + hi + (((hi - 10) >> 7) & -7));
-    ptr[1] = char(alphabase + lo + (((lo - 10) >> 7) & -7));
+    ptr[0] = char('0' + hi + (((9 - hi) >> 7) & alpha_shift));
+    ptr[1] = char('0' + lo + (((9 - lo) >> 7) & alpha_shift));
     ptr += 2;
     assert(ptr <= dest + dest_size);
   }
@@ -621,7 +659,7 @@ char *to_hex::write_bytes(char *__restrict const dest, size_t dest_size) const {
     MDBX_CXX20_LIKELY {
       ::std::ostream::sentry sentry(out);
       auto src = source.byte_ptr();
-      const char alphabase = (uppercase ? 'A' : 'a') - 10;
+      const char alpha_shift = (uppercase ? 'A' : 'a') - '9' - 1;
       unsigned width = 0;
       for (const auto end = source.end_byte_ptr(); src != end; ++src) {
         if (wrap_width && width >= wrap_width) {
@@ -630,8 +668,8 @@ char *to_hex::write_bytes(char *__restrict const dest, size_t dest_size) const {
         }
         const int8_t hi = *src >> 4;
         const int8_t lo = *src & 15;
-        out.put(char(alphabase + hi + (((hi - 10) >> 7) & -7)));
-        out.put(char(alphabase + lo + (((lo - 10) >> 7) & -7)));
+        out.put(char('0' + hi + (((9 - hi) >> 7) & alpha_shift)));
+        out.put(char('0' + lo + (((9 - lo) >> 7) & alpha_shift)));
         width += 2;
       }
     }
@@ -662,11 +700,11 @@ char *from_hex::write_bytes(char *__restrict const dest,
 
     int8_t hi = src[0];
     hi = (hi | 0x20) - 'a';
-    hi += 10 + ((hi >> 7) & 7);
+    hi += 10 + ((hi >> 7) & 39);
 
     int8_t lo = src[1];
     lo = (lo | 0x20) - 'a';
-    lo += 10 + ((lo >> 7) & 7);
+    lo += 10 + ((lo >> 7) & 39);
 
     *ptr++ = hi << 4 | lo;
     src += 2;
@@ -709,156 +747,135 @@ enum : signed char {
   IL /* invalid */ = -1
 };
 
-static const byte b58_alphabet[58] = {
-    '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F',
-    'G', 'H', 'J', 'K', 'L', 'M', 'N', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W',
-    'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'm',
-    'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z'};
-
-#ifndef bswap64
-#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
-static inline uint64_t bswap64(uint64_t v) noexcept {
-#if __GNUC_PREREQ(4, 4) || __CLANG_PREREQ(4, 0) ||                             \
-    __has_builtin(__builtin_bswap64)
-  return __builtin_bswap64(v);
-#elif defined(_MSC_VER) && !defined(__clang__)
-  return _byteswap_uint64(v);
-#elif defined(__bswap_64)
-  return __bswap_64(v);
-#elif defined(bswap_64)
-  return bswap_64(v);
+#if MDBX_WORDBITS > 32
+using b58_uint = uint_fast64_t;
 #else
-  return v << 56 | v >> 56 | ((v << 40) & UINT64_C(0x00ff000000000000)) |
-         ((v << 24) & UINT64_C(0x0000ff0000000000)) |
-         ((v << 8) & UINT64_C(0x000000ff00000000)) |
-         ((v >> 8) & UINT64_C(0x00000000ff000000)) |
-         ((v >> 24) & UINT64_C(0x0000000000ff0000)) |
-         ((v >> 40) & UINT64_C(0x000000000000ff00));
+using b58_uint = uint_fast32_t;
 #endif
-}
-#endif /* __BYTE_ORDER__ */
-#endif /* ifndef bswap64 */
 
-static inline char b58_8to11(uint64_t &v) noexcept {
-  const unsigned i = unsigned(v % 58);
+struct b58_buffer : public temp_buffer<b58_uint> {
+  b58_buffer(size_t bytes, size_t estimation_ratio_numerator,
+             size_t estimation_ratio_denominator, size_t extra = 0)
+      : temp_buffer((/* пересчитываем по указанной пропорции */
+                     bytes = (bytes * estimation_ratio_numerator +
+                              estimation_ratio_denominator - 1) /
+                             estimation_ratio_denominator,
+                     /* учитываем резервный старший байт в каждом слове */
+                     ((bytes + sizeof(b58_uint) - 2) / (sizeof(b58_uint) - 1) *
+                          sizeof(b58_uint) +
+                      extra) *
+                         sizeof(b58_uint))) {}
+};
+
+static byte b58_8to11(b58_uint &v) noexcept {
+  static const char b58_alphabet[58] = {
+      '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F',
+      'G', 'H', 'J', 'K', 'L', 'M', 'N', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W',
+      'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'm',
+      'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z'};
+
+  const auto i = size_t(v % 58);
   v /= 58;
   return b58_alphabet[i];
 }
 
+static slice b58_encode(b58_buffer &buf, const byte *begin, const byte *end) {
+  auto high = buf.end();
+  const auto modulo =
+      b58_uint((sizeof(b58_uint) > 4) ? UINT64_C(0x1A636A90B07A00) /* 58^9 */
+                                      : UINT32_C(0xACAD10) /* 58^4 */);
+  static_assert(sizeof(modulo) == 4 || sizeof(modulo) == 8, "WTF?");
+  while (begin < end) {
+    b58_uint carry = *begin++;
+    auto ptr = buf.end();
+    do {
+      assert(ptr > buf.area);
+      carry += *--ptr << CHAR_BIT;
+      *ptr = carry % modulo;
+      carry /= modulo;
+    } while (carry || ptr > high);
+    high = ptr;
+  }
+
+  byte *output = static_cast<byte *>(static_cast<void *>(buf.area));
+  auto ptr = output;
+  for (auto porous = high; porous < buf.end();) {
+    auto chunk = *porous++;
+    static_assert(sizeof(chunk) == 4 || sizeof(chunk) == 8, "WTF?");
+    assert(chunk < modulo);
+    if (sizeof(chunk) > 4) {
+      ptr[8] = b58_8to11(chunk);
+      ptr[7] = b58_8to11(chunk);
+      ptr[6] = b58_8to11(chunk);
+      ptr[5] = b58_8to11(chunk);
+      ptr[4] = b58_8to11(chunk);
+      ptr[3] = b58_8to11(chunk);
+      ptr[2] = b58_8to11(chunk);
+      ptr[1] = b58_8to11(chunk);
+      ptr[0] = b58_8to11(chunk);
+      ptr += 9;
+    } else {
+      ptr[3] = b58_8to11(chunk);
+      ptr[2] = b58_8to11(chunk);
+      ptr[1] = b58_8to11(chunk);
+      ptr[0] = b58_8to11(chunk);
+      ptr += 4;
+    }
+    assert(static_cast<void *>(ptr) < static_cast<void *>(porous));
+  }
+
+  while (output < ptr && *output == '1')
+    ++output;
+  return slice(output, ptr);
+}
+
 char *to_base58::write_bytes(char *__restrict const dest,
                              size_t dest_size) const {
   if (MDBX_UNLIKELY(envisage_result_length() > dest_size))
     MDBX_CXX20_UNLIKELY throw_too_small_target_buffer();
 
-  auto ptr = dest;
-  auto src = source.byte_ptr();
-  size_t left = source.length();
-  auto line = ptr;
-  while (MDBX_LIKELY(left > 7)) {
-    uint64_t v;
-    std::memcpy(&v, src, 8);
-    src += 8;
-#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
-    v = bswap64(v);
-#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
-#else
-#error "FIXME: Unsupported byte order"
-#endif /* __BYTE_ORDER__ */
-    ptr[10] = b58_8to11(v);
-    ptr[9] = b58_8to11(v);
-    ptr[8] = b58_8to11(v);
-    ptr[7] = b58_8to11(v);
-    ptr[6] = b58_8to11(v);
-    ptr[5] = b58_8to11(v);
-    ptr[4] = b58_8to11(v);
-    ptr[3] = b58_8to11(v);
-    ptr[2] = b58_8to11(v);
-    ptr[1] = b58_8to11(v);
-    ptr[0] = b58_8to11(v);
-    assert(v == 0);
-    ptr += 11;
-    left -= 8;
-    if (wrap_width && size_t(ptr - line) >= wrap_width && left) {
-      *ptr = '\n';
-      line = ++ptr;
-    }
-    assert(ptr <= dest + dest_size);
+  auto begin = source.byte_ptr();
+  auto end = source.end_byte_ptr();
+  line_wrapper wrapper(dest);
+  while (MDBX_LIKELY(begin < end) && *begin == 0) {
+    wrapper.put('1', wrap_width);
+    assert(wrapper.ptr <= dest + dest_size);
+    ++begin;
   }
 
-  if (left) {
-    uint64_t v = 0;
-    unsigned parrots = 31;
-    do {
-      v = (v << 8) + *src++;
-      parrots += 43;
-    } while (--left);
-
-    auto tail = ptr += parrots >> 5;
-    assert(ptr <= dest + dest_size);
-    do {
-      *--tail = b58_8to11(v);
-      parrots -= 32;
-    } while (parrots > 31);
-    assert(v == 0);
-  }
-
-  return ptr;
+  b58_buffer buf(end - begin, 11, 8);
+  wrapper.put(b58_encode(buf, begin, end), wrap_width);
+  return wrapper.ptr;
 }
 
 ::std::ostream &to_base58::output(::std::ostream &out) const {
   if (MDBX_LIKELY(!is_empty()))
     MDBX_CXX20_LIKELY {
       ::std::ostream::sentry sentry(out);
-      auto src = source.byte_ptr();
-      size_t left = source.length();
+      auto begin = source.byte_ptr();
+      auto end = source.end_byte_ptr();
       unsigned width = 0;
-      std::array<char, 11> buf;
-
-      while (MDBX_LIKELY(left > 7)) {
-        uint64_t v;
-        std::memcpy(&v, src, 8);
-        src += 8;
-#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
-        v = bswap64(v);
-#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
-#else
-#error "FIXME: Unsupported byte order"
-#endif /* __BYTE_ORDER__ */
-        buf[10] = b58_8to11(v);
-        buf[9] = b58_8to11(v);
-        buf[8] = b58_8to11(v);
-        buf[7] = b58_8to11(v);
-        buf[6] = b58_8to11(v);
-        buf[5] = b58_8to11(v);
-        buf[4] = b58_8to11(v);
-        buf[3] = b58_8to11(v);
-        buf[2] = b58_8to11(v);
-        buf[1] = b58_8to11(v);
-        buf[0] = b58_8to11(v);
-        assert(v == 0);
-        out.write(&buf.front(), 11);
-        left -= 8;
-        if (wrap_width && (width += 11) >= wrap_width && left) {
+      while (MDBX_LIKELY(begin < end) && *begin == 0) {
+        out.put('1');
+        if (wrap_width && ++width >= wrap_width) {
           out << ::std::endl;
           width = 0;
         }
+        ++begin;
       }
 
-      if (left) {
-        uint64_t v = 0;
-        unsigned parrots = 31;
-        do {
-          v = (v << 8) + *src++;
-          parrots += 43;
-        } while (--left);
-
-        auto ptr = buf.end();
-        do {
-          *--ptr = b58_8to11(v);
-          parrots -= 32;
-        } while (parrots > 31);
-        assert(v == 0);
-        out.write(&*ptr, buf.end() - ptr);
+      b58_buffer buf(end - begin, 11, 8);
+      const auto chunk = b58_encode(buf, begin, end);
+      if (!wrap_width || wrap_width > width + chunk.length())
+        out.write(chunk.char_ptr(), chunk.length());
+      else {
+        for (size_t i = 0; i < chunk.length(); ++i) {
+          out.put(chunk.char_ptr()[i]);
+          if (wrap_width && ++width >= wrap_width) {
+            out << ::std::endl;
+            width = 0;
+          }
+        }
       }
     }
   return out;
@@ -884,10 +901,46 @@ const signed char b58_map[256] = {
     IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL, IL  // f0
 };
 
-static inline signed char b58_11to8(uint64_t &v, const byte c) noexcept {
-  const signed char m = b58_map[c];
-  v = v * 58 + m;
-  return m;
+static slice b58_decode(b58_buffer &buf, const byte *begin, const byte *end,
+                        bool ignore_spaces) {
+  auto high = buf.end();
+  while (begin < end) {
+    const auto c = b58_map[*begin++];
+    if (MDBX_LIKELY(c >= 0)) {
+      b58_uint carry = c;
+      auto ptr = buf.end();
+      do {
+        assert(ptr > buf.area);
+        carry += *--ptr * 58;
+        *ptr = carry & (~b58_uint(0) >> CHAR_BIT);
+        carry >>= CHAR_BIT * (sizeof(carry) - 1);
+      } while (carry || ptr > high);
+      high = ptr;
+    } else if (MDBX_UNLIKELY(!ignore_spaces || !isspace(begin[-1])))
+      MDBX_CXX20_UNLIKELY
+    throw std::domain_error("mdbx::from_base58:: invalid base58 string");
+  }
+
+  byte *output = static_cast<byte *>(static_cast<void *>(buf.area));
+  auto ptr = output;
+  for (auto porous = high; porous < buf.end(); ++porous) {
+    auto chunk = *porous;
+    static_assert(sizeof(chunk) == 4 || sizeof(chunk) == 8, "WTF?");
+    assert(chunk <= (~b58_uint(0) >> CHAR_BIT));
+    if (sizeof(chunk) > 4) {
+      *ptr++ = byte(uint_fast64_t(chunk) >> CHAR_BIT * 6);
+      *ptr++ = byte(uint_fast64_t(chunk) >> CHAR_BIT * 5);
+      *ptr++ = byte(uint_fast64_t(chunk) >> CHAR_BIT * 4);
+      *ptr++ = byte(chunk >> CHAR_BIT * 3);
+    }
+    *ptr++ = byte(chunk >> CHAR_BIT * 2);
+    *ptr++ = byte(chunk >> CHAR_BIT * 1);
+    *ptr++ = byte(chunk >> CHAR_BIT * 0);
+  }
+
+  while (output < ptr && *output == 0)
+    ++output;
+  return slice(output, ptr);
 }
 
 char *from_base58::write_bytes(char *__restrict const dest,
@@ -896,98 +949,33 @@ char *from_base58::write_bytes(char *__restrict const dest,
     MDBX_CXX20_UNLIKELY throw_too_small_target_buffer();
 
   auto ptr = dest;
-  auto src = source.byte_ptr();
-  for (auto left = source.length(); left > 0;) {
-    if (MDBX_UNLIKELY(isspace(*src)) && ignore_spaces) {
-      ++src;
-      --left;
-      continue;
-    }
-
-    if (MDBX_LIKELY(left > 10)) {
-      uint64_t v = 0;
-      if (MDBX_UNLIKELY((b58_11to8(v, src[0]) | b58_11to8(v, src[1]) |
-                         b58_11to8(v, src[2]) | b58_11to8(v, src[3]) |
-                         b58_11to8(v, src[4]) | b58_11to8(v, src[5]) |
-                         b58_11to8(v, src[6]) | b58_11to8(v, src[7]) |
-                         b58_11to8(v, src[8]) | b58_11to8(v, src[9]) |
-                         b58_11to8(v, src[10])) < 0))
-        MDBX_CXX20_UNLIKELY goto bailout;
-#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
-      v = bswap64(v);
-#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
-#else
-#error "FIXME: Unsupported byte order"
-#endif /* __BYTE_ORDER__ */
-      std::memcpy(ptr, &v, 8);
-      ptr += 8;
-      src += 11;
-      left -= 11;
-      assert(ptr <= dest + dest_size);
-      continue;
-    }
-
-    constexpr unsigned invalid_length_mask = 1 << 1 | 1 << 4 | 1 << 8;
-    if (MDBX_UNLIKELY(invalid_length_mask & (1 << left)))
-      MDBX_CXX20_UNLIKELY goto bailout;
-
-    uint64_t v = 1;
-    unsigned parrots = 0;
-    do {
-      if (MDBX_UNLIKELY(b58_11to8(v, *src++) < 0))
-        MDBX_CXX20_UNLIKELY goto bailout;
-      parrots += 32;
-    } while (--left);
-
-    auto tail = ptr += parrots / 43;
-    assert(ptr <= dest + dest_size);
-    do {
-      *--tail = byte(v);
-      v >>= 8;
-    } while (v > 255);
-    break;
+  auto begin = source.byte_ptr();
+  auto const end = source.end_byte_ptr();
+  while (begin < end && *begin <= '1') {
+    if (MDBX_LIKELY(*begin == '1'))
+      MDBX_CXX20_LIKELY *ptr++ = 0;
+    else if (MDBX_UNLIKELY(!ignore_spaces || !isspace(*begin)))
+      MDBX_CXX20_UNLIKELY
+    throw std::domain_error("mdbx::from_base58:: invalid base58 string");
+    ++begin;
   }
-  return ptr;
 
-bailout:
-  throw std::domain_error("mdbx::from_base58:: invalid base58 string");
+  b58_buffer buf(end - begin, 47, 64);
+  auto slice = b58_decode(buf, begin, end, ignore_spaces);
+  memcpy(ptr, slice.data(), slice.length());
+  return ptr + slice.length();
 }
 
 bool from_base58::is_erroneous() const noexcept {
-  bool got = false;
-  auto src = source.byte_ptr();
-  for (auto left = source.length(); left > 0;) {
-    if (MDBX_UNLIKELY(*src <= ' ') &&
-        MDBX_LIKELY(ignore_spaces && isspace(*src))) {
-      ++src;
-      --left;
-      continue;
-    }
-
-    if (MDBX_LIKELY(left > 10)) {
-      if (MDBX_UNLIKELY((b58_map[src[0]] | b58_map[src[1]] | b58_map[src[2]] |
-                         b58_map[src[3]] | b58_map[src[4]] | b58_map[src[5]] |
-                         b58_map[src[6]] | b58_map[src[7]] | b58_map[src[8]] |
-                         b58_map[src[9]] | b58_map[src[10]]) < 0))
-        MDBX_CXX20_UNLIKELY return true;
-      src += 11;
-      left -= 11;
-      got = true;
-      continue;
-    }
-
-    constexpr unsigned invalid_length_mask = 1 << 1 | 1 << 4 | 1 << 8;
-    if (invalid_length_mask & (1 << left))
-      return false;
-
-    do
-      if (MDBX_UNLIKELY(b58_map[*src++] < 0))
-        MDBX_CXX20_UNLIKELY return true;
-    while (--left);
-    got = true;
-    break;
+  auto begin = source.byte_ptr();
+  auto const end = source.end_byte_ptr();
+  while (begin < end) {
+    if (MDBX_UNLIKELY(b58_map[*begin] < 0 &&
+                      !(ignore_spaces && isspace(*begin))))
+      return true;
+    ++begin;
   }
-  return !got;
+  return false;
 }
 
 //------------------------------------------------------------------------------
diff --git a/src/options.h b/src/options.h
index 0ef27e6f..19a7cb32 100644
--- a/src/options.h
+++ b/src/options.h
@@ -28,9 +28,17 @@
 #define MDBX_OSX_SPEED_INSTEADOF_DURABILITY MDBX_OSX_WANNA_DURABILITY
 #endif /* MDBX_OSX_SPEED_INSTEADOF_DURABILITY */
 
+/** Controls using of POSIX' madvise() and/or similar hints. */
+#ifndef MDBX_ENABLE_MADVISE
+#define MDBX_ENABLE_MADVISE 1
+#elif !(MDBX_ENABLE_MADVISE == 0 || MDBX_ENABLE_MADVISE == 1)
+#error MDBX_ENABLE_MADVISE must be defined as 0 or 1
+#endif /* MDBX_ENABLE_MADVISE */
+
 /** Controls checking PID against reuse DB environment after the fork() */
 #ifndef MDBX_ENV_CHECKPID
-#if defined(MADV_DONTFORK) || defined(_WIN32) || defined(_WIN64)
+#if (defined(MADV_DONTFORK) && MDBX_ENABLE_MADVISE) || defined(_WIN32) ||      \
+    defined(_WIN64)
 /* PID check could be omitted:
  *  - on Linux when madvise(MADV_DONTFORK) is available, i.e. after the fork()
  *    mapped pages will not be available for child process.
@@ -96,8 +104,7 @@
 /** Controls using Unix' mincore() to determine whether DB-pages
  * are resident in memory. */
 #ifndef MDBX_ENABLE_MINCORE
-#if MDBX_ENABLE_PREFAULT &&                                                    \
-    (defined(MINCORE_INCORE) || !(defined(_WIN32) || defined(_WIN64)))
+#if defined(MINCORE_INCORE) || !(defined(_WIN32) || defined(_WIN64))
 #define MDBX_ENABLE_MINCORE 1
 #else
 #define MDBX_ENABLE_MINCORE 0
@@ -118,13 +125,6 @@
 #error MDBX_ENABLE_BIGFOOT must be defined as 0 or 1
 #endif /* MDBX_ENABLE_BIGFOOT */
 
-/** Controls using of POSIX' madvise() and/or similar hints. */
-#ifndef MDBX_ENABLE_MADVISE
-#define MDBX_ENABLE_MADVISE 1
-#elif !(MDBX_ENABLE_MADVISE == 0 || MDBX_ENABLE_MADVISE == 1)
-#error MDBX_ENABLE_MADVISE must be defined as 0 or 1
-#endif /* MDBX_ENABLE_MADVISE */
-
 /** Disable some checks to reduce an overhead and detection probability of
  * database corruption to a values closer to the LMDB. */
 #ifndef MDBX_DISABLE_VALIDATION
diff --git a/test/config.c++ b/test/config.c++
index 31cf9395..922f7b37 100644
--- a/test/config.c++
+++ b/test/config.c++
@@ -667,7 +667,10 @@ bool actor_config::deserialize(const char *str, actor_config &config) {
   }
   str = slash + 1;
 
-  uint64_t verify = std::stoull(std::string(str));
+  uint64_t verify = 0;
+  while (*str >= '0' && *str <= '9')
+    verify = verify * 10 + *str++ - '0';
+
   if (checksum.value != verify) {
     TRACE("<< actor_config::deserialize: checksum mismatch\n");
     return false;