diff --git a/.github/workflows/data/core/tracked.txt b/.github/workflows/data/core/tracked.txt
index 5b2a3ca4d..855cb884e 100644
--- a/.github/workflows/data/core/tracked.txt
+++ b/.github/workflows/data/core/tracked.txt
@@ -3,6 +3,5 @@ onetl/plugins/**
 onetl/impl/**
 onetl/hwm/**
 onetl/_util/**
-onetl/_internal.py
 onetl/log.py
 .github/workflows/data/core/**
diff --git a/.github/workflows/test-core.yml b/.github/workflows/test-core.yml
index 65d681dc1..6008f9250 100644
--- a/.github/workflows/test-core.yml
+++ b/.github/workflows/test-core.yml
@@ -72,7 +72,7 @@ jobs:
       - name: Run tests
         run: |
           ./run_tests.sh -m 'not connection'
-          ./run_tests.sh onetl/_util onetl/_internal.py onetl/hooks onetl/file/filter onetl/file/limit onetl/hwm/store/hwm_class_registry.py
+          ./run_tests.sh onetl/_util onetl/hooks onetl/file/filter onetl/file/limit onetl/hwm/store/hwm_class_registry.py
 
       - name: Upload coverage results
         uses: actions/upload-artifact@v4
diff --git a/onetl/_internal.py b/onetl/_internal.py
deleted file mode 100644
index 361bb3e82..000000000
--- a/onetl/_internal.py
+++ /dev/null
@@ -1,172 +0,0 @@
-# SPDX-FileCopyrightText: 2021-2024 MTS (Mobile Telesystems)
-# SPDX-License-Identifier: Apache-2.0
-"""
-    Helpers
-"""
-
-from __future__ import annotations
-
-import os
-from datetime import datetime
-from typing import TYPE_CHECKING, Any
-
-try:
-    from pydantic.v1 import SecretStr
-except (ImportError, AttributeError):
-    from pydantic import SecretStr  # type: ignore[no-redef, assignment]
-
-if TYPE_CHECKING:
-    from pathlib import PurePath
-
-# e.g. 20230524122150
-DATETIME_FORMAT = "%Y%m%d%H%M%S"
-
-
-def clear_statement(statement: str) -> str:
-    """
-    Clear unnecessary spaces and semicolons at the statement end.
-
-    Oracle-specific: adds semicolon after END statement.
-
-    Examples
-    --------
-
-    >>> clear_statement("SELECT * FROM mytable")
-    'SELECT * FROM mytable'
-    >>> clear_statement("SELECT * FROM mytable ; ")
-    'SELECT * FROM mytable'
-    >>> clear_statement("CREATE TABLE mytable (id NUMBER)")
-    'CREATE TABLE mytable (id NUMBER)'
-    >>> clear_statement("BEGIN ... END")
-    'BEGIN ... END;'
-    """
-
-    statement = statement.rstrip().lstrip("\n\r").rstrip(";").rstrip()
-    if statement.lower().endswith("end"):
-        statement += ";"
-    return statement
-
-
-def uniq_ignore_case(orig_list: list[str]) -> list[str]:
-    """
-    Return only uniq values from a list, case ignore.
-
-    Examples
-    --------
-
-    >>> uniq_ignore_case(["a", "c"])
-    ['a', 'c']
-    >>> uniq_ignore_case(["A", "a", "c"])
-    ['A', 'c']
-    >>> uniq_ignore_case(["a", "A", "c"])
-    ['a', 'c']
-    """
-
-    result: list[str] = []
-    already_visited: set[str] = set()
-
-    for orig_value in orig_list:
-        if orig_value.casefold() not in already_visited:
-            result.append(orig_value)
-            already_visited.add(orig_value.casefold())
-
-    return result
-
-
-def stringify(value: Any, quote: bool = False) -> Any:  # noqa: WPS212
-    """
-    Convert values to strings.
-
-    Values ``True``, ``False`` and ``None`` become ``"true"``, ``"false"`` and ``"null"``.
-
-    If input is dict, return dict with stringified values and keys (recursive).
-
-    If input is list, return list with stringified values (recursive).
-
-    If ``quote=True``, wrap string values with double quotes.
-
-    Examples
-    --------
-
-    >>> stringify(1)
-    '1'
-    >>> stringify(True)
-    'true'
-    >>> stringify(False)
-    'false'
-    >>> stringify(None)
-    'null'
-    >>> stringify("string")
-    'string'
-    >>> stringify("string", quote=True)
-    '"string"'
-    >>> stringify({"abc": 1})
-    {'abc': '1'}
-    >>> stringify([1, True, False, None, "string"])
-    ['1', 'true', 'false', 'null', 'string']
-    """
-
-    if isinstance(value, dict):
-        return {stringify(k): stringify(v, quote) for k, v in value.items()}
-
-    if isinstance(value, list):
-        return [stringify(v, quote) for v in value]
-
-    if value is None:
-        return "null"
-
-    if isinstance(value, bool):
-        return "true" if value else "false"
-
-    if isinstance(value, SecretStr):
-        value = value.get_secret_value()
-
-    if isinstance(value, os.PathLike):
-        value = os.fspath(value)
-
-    if isinstance(value, str):
-        return f'"{value}"' if quote else value
-
-    return str(value)
-
-
-def to_camel(string: str) -> str:
-    """
-    Convert ``snake_case`` strings to ``camelCase`` (with first symbol in lowercase)
-
-    Examples
-    --------
-
-    >>> to_camel("some_value")
-    'someValue'
-    """
-
-    return "".join(word.capitalize() if index > 0 else word for index, word in enumerate(string.split("_")))
-
-
-def generate_temp_path(root: PurePath) -> PurePath:
-    """
-    Returns prefix which will be used for creating temp directory
-
-    Returns
-    -------
-    RemotePath
-        Temp path, containing current host name, process name and datetime
-
-    Examples
-    --------
-
-    >>> from etl_entities.process import Process
-    >>> from pathlib import Path
-    >>> generate_temp_path(Path("/tmp")) # doctest: +SKIP
-    Path("/tmp/onetl/currenthost/myprocess/20230524122150")
-    >>> with Process(dag="mydag", task="mytask"): # doctest: +SKIP
-    ...    generate_temp_path(Path("/abc"))
-    Path("/abc/onetl/currenthost/mydag.mytask.myprocess/20230524122150")
-    """
-
-    from etl_entities.process import ProcessStackManager
-
-    current_process = ProcessStackManager.get_current()
-    current_dt = datetime.now().strftime(DATETIME_FORMAT)
-    return root / "onetl" / current_process.host / current_process.full_name / current_dt
diff --git a/onetl/_util/file.py b/onetl/_util/file.py
index 06e6ef047..ee27c57f4 100644
--- a/onetl/_util/file.py
+++ b/onetl/_util/file.py
@@ -5,11 +5,15 @@
 import hashlib
 import io
 import os
-from pathlib import Path
+from datetime import datetime
+from pathlib import Path, PurePath
 
 from onetl.exception import NotAFileError
 from onetl.impl import path_repr
 
+# e.g. 20230524122150
+DATETIME_FORMAT = "%Y%m%d%H%M%S"
+
 
 def get_file_hash(
     path: os.PathLike | str,
@@ -41,3 +45,31 @@ def is_file_readable(path: str | os.PathLike) -> Path:
         raise OSError(f"No read access to file {path_repr(path)}")
 
     return path
+
+
+def generate_temp_path(root: PurePath) -> PurePath:
+    """
+    Returns prefix which will be used for creating temp directory
+
+    Returns
+    -------
+    RemotePath
+        Temp path, containing current host name, process name and datetime
+
+    Examples
+    --------
+
+    >>> from etl_entities.process import Process
+    >>> from pathlib import Path
+    >>> generate_temp_path(Path("/tmp")) # doctest: +SKIP
+    Path("/tmp/onetl/currenthost/myprocess/20230524122150")
+    >>> with Process(dag="mydag", task="mytask"): # doctest: +SKIP
+    ...    generate_temp_path(Path("/abc"))
+    Path("/abc/onetl/currenthost/mydag.mytask.myprocess/20230524122150")
+    """
+
+    from etl_entities.process import ProcessStackManager
+
+    current_process = ProcessStackManager.get_current()
+    current_dt = datetime.now().strftime(DATETIME_FORMAT)
+    return root / "onetl" / current_process.host / current_process.full_name / current_dt
diff --git a/onetl/_util/spark.py b/onetl/_util/spark.py
index 230abe80e..f172b1c98 100644
--- a/onetl/_util/spark.py
+++ b/onetl/_util/spark.py
@@ -2,6 +2,7 @@
 # SPDX-License-Identifier: Apache-2.0
 from __future__ import annotations
 
+import os
 import textwrap
 from contextlib import contextmanager
 from math import inf
@@ -9,11 +10,73 @@
 
 from onetl._util.version import Version
 
+try:
+    from pydantic.v1 import SecretStr
+except (ImportError, AttributeError):
+    from pydantic import SecretStr  # type: ignore[no-redef, assignment]
+
 if TYPE_CHECKING:
     from pyspark.sql import SparkSession
     from pyspark.sql.conf import RuntimeConfig
 
 
+def stringify(value: Any, quote: bool = False) -> Any:  # noqa: WPS212
+    """
+    Convert values to strings.
+
+    Values ``True``, ``False`` and ``None`` become ``"true"``, ``"false"`` and ``"null"``.
+
+    If input is dict, return dict with stringified values and keys (recursive).
+
+    If input is list, return list with stringified values (recursive).
+
+    If ``quote=True``, wrap string values with double quotes.
+
+    Examples
+    --------
+
+    >>> stringify(1)
+    '1'
+    >>> stringify(True)
+    'true'
+    >>> stringify(False)
+    'false'
+    >>> stringify(None)
+    'null'
+    >>> stringify("string")
+    'string'
+    >>> stringify("string", quote=True)
+    '"string"'
+    >>> stringify({"abc": 1})
+    {'abc': '1'}
+    >>> stringify([1, True, False, None, "string"])
+    ['1', 'true', 'false', 'null', 'string']
+    """
+
+    if isinstance(value, dict):
+        return {stringify(k): stringify(v, quote) for k, v in value.items()}
+
+    if isinstance(value, list):
+        return [stringify(v, quote) for v in value]
+
+    if value is None:
+        return "null"
+
+    if isinstance(value, bool):
+        return "true" if value else "false"
+
+    if isinstance(value, SecretStr):
+        value = value.get_secret_value()
+
+    if isinstance(value, os.PathLike):
+        value = os.fspath(value)
+
+    if isinstance(value, str):
+        return f'"{value}"' if quote else value
+
+    return str(value)
+
+
 @contextmanager
 def inject_spark_param(conf: RuntimeConfig, name: str, value: Any):
     """
diff --git a/onetl/_util/sql.py b/onetl/_util/sql.py
new file mode 100644
index 000000000..37aa09a78
--- /dev/null
+++ b/onetl/_util/sql.py
@@ -0,0 +1,25 @@
+# SPDX-FileCopyrightText: 2021-2024 MTS (Mobile Telesystems)
+# SPDX-License-Identifier: Apache-2.0
+def clear_statement(statement: str) -> str:
+    """
+    Clear unnecessary spaces and semicolons at the statement end.
+
+    Oracle-specific: adds semicolon after END statement.
+
+    Examples
+    --------
+
+    >>> clear_statement("SELECT * FROM mytable")
+    'SELECT * FROM mytable'
+    >>> clear_statement("SELECT * FROM mytable ; ")
+    'SELECT * FROM mytable'
+    >>> clear_statement("CREATE TABLE mytable (id NUMBER)")
+    'CREATE TABLE mytable (id NUMBER)'
+    >>> clear_statement("BEGIN ... END")
+    'BEGIN ... END;'
+    """
+
+    statement = statement.rstrip().lstrip("\n\r").rstrip(";").rstrip()
+    if statement.lower().endswith("end"):
+        statement += ";"
+    return statement
diff --git a/onetl/connection/db_connection/hive/connection.py b/onetl/connection/db_connection/hive/connection.py
index fbedebefa..7fcb4dce2 100644
--- a/onetl/connection/db_connection/hive/connection.py
+++ b/onetl/connection/db_connection/hive/connection.py
@@ -13,8 +13,8 @@
 except (ImportError, AttributeError):
     from pydantic import validator  # type: ignore[no-redef, assignment]
 
-from onetl._internal import clear_statement
 from onetl._util.spark import inject_spark_param
+from onetl._util.sql import clear_statement
 from onetl.connection.db_connection.db_connection import DBConnection
 from onetl.connection.db_connection.hive.dialect import HiveDialect
 from onetl.connection.db_connection.hive.options import (
diff --git a/onetl/connection/db_connection/jdbc_connection/connection.py b/onetl/connection/db_connection/jdbc_connection/connection.py
index e6716ae5e..5b0aebeb8 100644
--- a/onetl/connection/db_connection/jdbc_connection/connection.py
+++ b/onetl/connection/db_connection/jdbc_connection/connection.py
@@ -7,7 +7,7 @@
 import warnings
 from typing import TYPE_CHECKING, Any
 
-from onetl._internal import clear_statement
+from onetl._util.sql import clear_statement
 from onetl.connection.db_connection.db_connection import DBConnection
 from onetl.connection.db_connection.jdbc_connection.dialect import JDBCDialect
 from onetl.connection.db_connection.jdbc_connection.options import (
diff --git a/onetl/connection/db_connection/jdbc_connection/options.py b/onetl/connection/db_connection/jdbc_connection/options.py
index cd4538f29..a2aa39adb 100644
--- a/onetl/connection/db_connection/jdbc_connection/options.py
+++ b/onetl/connection/db_connection/jdbc_connection/options.py
@@ -15,7 +15,6 @@
 
 from typing_extensions import deprecated
 
-from onetl._internal import to_camel
 from onetl.impl import GenericOptions
 
 # options from spark.read.jdbc which are populated by JDBCConnection methods
@@ -144,10 +143,9 @@ class Config:
         known_options = READ_OPTIONS | READ_WRITE_OPTIONS
         prohibited_options = GENERIC_PROHIBITED_OPTIONS | WRITE_OPTIONS
         extra = "allow"
-        alias_generator = to_camel
 
     # Options in DataFrameWriter.jdbc() method
-    partition_column: Optional[str] = None
+    partition_column: Optional[str] = Field(default=None, alias="partitionColumn")
     """Column used to parallelize reading from a table.
 
     .. warning::
@@ -164,17 +162,17 @@ class Config:
 
     See documentation for :obj:`~partitioning_mode` for more details"""
 
-    num_partitions: PositiveInt = 1
+    num_partitions: PositiveInt = Field(default=1, alias="numPartitions")
     """Number of jobs created by Spark to read the table content in parallel.
     See documentation for :obj:`~partitioning_mode` for more details"""
 
-    lower_bound: Optional[int] = None
+    lower_bound: Optional[int] = Field(default=None, alias="lowerBound")
     """See documentation for :obj:`~partitioning_mode` for more details"""  # noqa: WPS322
 
-    upper_bound: Optional[int] = None
+    upper_bound: Optional[int] = Field(default=None, alias="upperBound")
     """See documentation for :obj:`~partitioning_mode` for more details"""  # noqa: WPS322
 
-    session_init_statement: Optional[str] = None
+    session_init_statement: Optional[str] = Field(default=None, alias="sessionInitStatement")
     '''After each database session is opened to the remote DB and before starting to read data,
     this option executes a custom SQL statement (or a PL/SQL block).
 
@@ -423,7 +421,6 @@ class Config:
         known_options = WRITE_OPTIONS | READ_WRITE_OPTIONS
         prohibited_options = GENERIC_PROHIBITED_OPTIONS | READ_OPTIONS
         extra = "allow"
-        alias_generator = to_camel
 
     if_exists: JDBCTableExistBehavior = Field(default=JDBCTableExistBehavior.APPEND, alias="mode")
     """Behavior of writing data into existing table.
@@ -528,7 +525,7 @@ class Config:
         Changed default value from 1000 to 20_000
     """
 
-    isolation_level: str = "READ_UNCOMMITTED"
+    isolation_level: str = Field(default="READ_UNCOMMITTED", alias="isolationLevel")
     """The transaction isolation level, which applies to current connection.
 
     Possible values:
@@ -571,7 +568,7 @@ class JDBCSQLOptions(GenericOptions):
         Split up ``ReadOptions`` to ``SQLOptions``
     """
 
-    partition_column: Optional[str] = None
+    partition_column: Optional[str] = Field(default=None, alias="partitionColumn")
     """Column used to partition data across multiple executors for parallel query processing.
 
     .. warning::
@@ -600,16 +597,16 @@ class JDBCSQLOptions(GenericOptions):
         -- Where ``stride`` is calculated as ``(upper_bound - lower_bound) / num_partitions``.
     """
 
-    num_partitions: Optional[int] = None
+    num_partitions: Optional[int] = Field(default=None, alias="numPartitions")
     """Number of jobs created by Spark to read the table content in parallel."""  # noqa: WPS322
 
-    lower_bound: Optional[int] = None
+    lower_bound: Optional[int] = Field(default=None, alias="lowerBound")
     """Defines the starting boundary for partitioning the query's data. Mandatory if :obj:`~partition_column` is set"""  # noqa: WPS322
 
-    upper_bound: Optional[int] = None
+    upper_bound: Optional[int] = Field(default=None, alias="upperBound")
     """Sets the ending boundary for data partitioning. Mandatory if :obj:`~partition_column` is set"""  # noqa: WPS322
 
-    session_init_statement: Optional[str] = None
+    session_init_statement: Optional[str] = Field(default=None, alias="sessionInitStatement")
     '''After each database session is opened to the remote DB and before starting to read data,
     this option executes a custom SQL statement (or a PL/SQL block).
 
@@ -658,7 +655,6 @@ class Config:
         known_options = READ_OPTIONS - {"partitioning_mode"}
         prohibited_options = GENERIC_PROHIBITED_OPTIONS | WRITE_OPTIONS | {"partitioning_mode"}
         extra = "allow"
-        alias_generator = to_camel
 
     @root_validator(pre=True)
     def _check_partition_fields(cls, values):
diff --git a/onetl/connection/db_connection/jdbc_mixin/connection.py b/onetl/connection/db_connection/jdbc_mixin/connection.py
index 8ab430751..e8c19e38b 100644
--- a/onetl/connection/db_connection/jdbc_mixin/connection.py
+++ b/onetl/connection/db_connection/jdbc_mixin/connection.py
@@ -16,9 +16,9 @@
 except (ImportError, AttributeError):
     from pydantic import Field, PrivateAttr, SecretStr, validator  # type: ignore[no-redef, assignment]
 
-from onetl._internal import clear_statement, stringify
 from onetl._util.java import get_java_gateway, try_import_java_class
-from onetl._util.spark import get_spark_version
+from onetl._util.spark import get_spark_version, stringify
+from onetl._util.sql import clear_statement
 from onetl._util.version import Version
 from onetl.connection.db_connection.jdbc_mixin.options import (
     JDBCExecuteOptions,
diff --git a/onetl/connection/db_connection/kafka/connection.py b/onetl/connection/db_connection/kafka/connection.py
index b64fff143..ce3829e49 100644
--- a/onetl/connection/db_connection/kafka/connection.py
+++ b/onetl/connection/db_connection/kafka/connection.py
@@ -14,10 +14,9 @@
 except (ImportError, AttributeError):
     from pydantic import root_validator, validator  # type: ignore[no-redef, assignment]
 
-from onetl._internal import stringify
 from onetl._util.java import try_import_java_class
 from onetl._util.scala import get_default_scala_version
-from onetl._util.spark import get_spark_version
+from onetl._util.spark import get_spark_version, stringify
 from onetl._util.version import Version
 from onetl.connection.db_connection.db_connection import DBConnection
 from onetl.connection.db_connection.kafka.dialect import KafkaDialect
diff --git a/onetl/connection/db_connection/kafka/kafka_kerberos_auth.py b/onetl/connection/db_connection/kafka/kafka_kerberos_auth.py
index 6a20a31af..40e9aa55a 100644
--- a/onetl/connection/db_connection/kafka/kafka_kerberos_auth.py
+++ b/onetl/connection/db_connection/kafka/kafka_kerberos_auth.py
@@ -12,8 +12,8 @@
 except (ImportError, AttributeError):
     from pydantic import Field, PrivateAttr, root_validator, validator  # type: ignore[no-redef, assignment]
 
-from onetl._internal import stringify
 from onetl._util.file import get_file_hash, is_file_readable
+from onetl._util.spark import stringify
 from onetl.connection.db_connection.kafka.kafka_auth import KafkaAuth
 from onetl.impl import GenericOptions, LocalPath, path_repr
 
diff --git a/onetl/connection/db_connection/kafka/kafka_scram_auth.py b/onetl/connection/db_connection/kafka/kafka_scram_auth.py
index add09f349..823d0f82f 100644
--- a/onetl/connection/db_connection/kafka/kafka_scram_auth.py
+++ b/onetl/connection/db_connection/kafka/kafka_scram_auth.py
@@ -11,7 +11,7 @@
 
 from typing_extensions import Literal
 
-from onetl._internal import stringify
+from onetl._util.spark import stringify
 from onetl.connection.db_connection.kafka.kafka_auth import KafkaAuth
 from onetl.impl import GenericOptions
 
diff --git a/onetl/connection/db_connection/kafka/kafka_ssl_protocol.py b/onetl/connection/db_connection/kafka/kafka_ssl_protocol.py
index 6149f5aa0..24dd52f6e 100644
--- a/onetl/connection/db_connection/kafka/kafka_ssl_protocol.py
+++ b/onetl/connection/db_connection/kafka/kafka_ssl_protocol.py
@@ -10,8 +10,8 @@
 except (ImportError, AttributeError):
     from pydantic import Field, SecretStr, validator  # type: ignore[no-redef, assignment]
 
-from onetl._internal import stringify
 from onetl._util.file import is_file_readable
+from onetl._util.spark import stringify
 from onetl.impl import GenericOptions, LocalPath
 
 if TYPE_CHECKING:
diff --git a/onetl/connection/db_connection/oracle/connection.py b/onetl/connection/db_connection/oracle/connection.py
index 8ca1b6ef1..043989500 100644
--- a/onetl/connection/db_connection/oracle/connection.py
+++ b/onetl/connection/db_connection/oracle/connection.py
@@ -19,8 +19,8 @@
 
 from etl_entities.instance import Host
 
-from onetl._internal import clear_statement
 from onetl._util.classproperty import classproperty
+from onetl._util.sql import clear_statement
 from onetl._util.version import Version
 from onetl.connection.db_connection.jdbc_connection import JDBCConnection
 from onetl.connection.db_connection.jdbc_connection.options import JDBCReadOptions
diff --git a/onetl/connection/db_connection/teradata/connection.py b/onetl/connection/db_connection/teradata/connection.py
index d6ea76acc..6ef2637b4 100644
--- a/onetl/connection/db_connection/teradata/connection.py
+++ b/onetl/connection/db_connection/teradata/connection.py
@@ -7,8 +7,8 @@
 
 from etl_entities.instance import Host
 
-from onetl._internal import stringify
 from onetl._util.classproperty import classproperty
+from onetl._util.spark import stringify
 from onetl._util.version import Version
 from onetl.connection.db_connection.jdbc_connection import JDBCConnection
 from onetl.connection.db_connection.teradata.dialect import TeradataDialect
diff --git a/onetl/connection/file_df_connection/spark_s3/connection.py b/onetl/connection/file_df_connection/spark_s3/connection.py
index 04da89e0e..1efe39d4e 100644
--- a/onetl/connection/file_df_connection/spark_s3/connection.py
+++ b/onetl/connection/file_df_connection/spark_s3/connection.py
@@ -16,11 +16,10 @@
 
 from typing_extensions import Literal
 
-from onetl._internal import stringify
 from onetl._util.hadoop import get_hadoop_config, get_hadoop_version
 from onetl._util.java import try_import_java_class
 from onetl._util.scala import get_default_scala_version
-from onetl._util.spark import get_spark_version
+from onetl._util.spark import get_spark_version, stringify
 from onetl._util.version import Version
 from onetl.base import (
     BaseReadableFileFormat,
diff --git a/onetl/file/file_downloader/file_downloader.py b/onetl/file/file_downloader/file_downloader.py
index 3fe45ff40..069f8c69b 100644
--- a/onetl/file/file_downloader/file_downloader.py
+++ b/onetl/file/file_downloader/file_downloader.py
@@ -22,7 +22,7 @@
 except (ImportError, AttributeError):
     from pydantic import Field, PrivateAttr, root_validator, validator  # type: ignore[no-redef, assignment]
 
-from onetl._internal import generate_temp_path
+from onetl._util.file import generate_temp_path
 from onetl.base import BaseFileConnection, BaseFileFilter, BaseFileLimit
 from onetl.base.path_protocol import PathProtocol
 from onetl.file.file_downloader.options import FileDownloaderOptions
diff --git a/onetl/file/file_uploader/file_uploader.py b/onetl/file/file_uploader/file_uploader.py
index 9ab5f088f..fc6709ce3 100644
--- a/onetl/file/file_uploader/file_uploader.py
+++ b/onetl/file/file_uploader/file_uploader.py
@@ -15,7 +15,7 @@
 except (ImportError, AttributeError):
     from pydantic import PrivateAttr, validator  # type: ignore[no-redef, assignment]
 
-from onetl._internal import generate_temp_path
+from onetl._util.file import generate_temp_path
 from onetl.base import BaseFileConnection
 from onetl.base.path_protocol import PathWithStatsProtocol
 from onetl.base.pure_path_protocol import PurePathProtocol
diff --git a/onetl/file/format/csv.py b/onetl/file/format/csv.py
index 353a8e987..1c4442fd5 100644
--- a/onetl/file/format/csv.py
+++ b/onetl/file/format/csv.py
@@ -10,8 +10,7 @@
 except (ImportError, AttributeError):
     from pydantic import Field  # type: ignore[no-redef, assignment]
 
-from onetl._internal import stringify
-from onetl._util.spark import get_spark_version
+from onetl._util.spark import get_spark_version, stringify
 from onetl.file.format.file_format import ReadWriteFileFormat
 from onetl.hooks import slot, support_hooks
 
diff --git a/onetl/file/format/json.py b/onetl/file/format/json.py
index 698874424..085d125e4 100644
--- a/onetl/file/format/json.py
+++ b/onetl/file/format/json.py
@@ -6,7 +6,7 @@
 
 from typing_extensions import Literal
 
-from onetl._internal import stringify
+from onetl._util.spark import stringify
 from onetl.file.format.file_format import ReadOnlyFileFormat
 from onetl.hooks import slot, support_hooks
 
diff --git a/tests/tests_unit/test_internal_unit/test_generate_temp_path.py b/tests/tests_unit/test_internal_unit/test_generate_temp_path.py
index faad170fe..0b8f98853 100644
--- a/tests/tests_unit/test_internal_unit/test_generate_temp_path.py
+++ b/tests/tests_unit/test_internal_unit/test_generate_temp_path.py
@@ -3,13 +3,14 @@
 from pathlib import PurePath
 
 import pytest
-from etl_entities.process import Process
 
-from onetl._internal import generate_temp_path
+from onetl._util.file import generate_temp_path
 
 
 @pytest.mark.flaky(reruns=5)
 def test_generate_temp_path():
+    from etl_entities.process import Process
+
     root = PurePath("/path")
 
     dt_prefix = datetime.now().strftime("%Y%m%d%H%M")  # up to minutes, not seconds
diff --git a/tests/tests_unit/tests_db_connection_unit/test_jdbc_options_unit.py b/tests/tests_unit/tests_db_connection_unit/test_jdbc_options_unit.py
index 699838889..6d3ff1322 100644
--- a/tests/tests_unit/tests_db_connection_unit/test_jdbc_options_unit.py
+++ b/tests/tests_unit/tests_db_connection_unit/test_jdbc_options_unit.py
@@ -2,7 +2,6 @@
 
 import pytest
 
-from onetl._internal import to_camel
 from onetl.connection import MSSQL, Clickhouse, MySQL, Oracle, Postgres, Teradata
 from onetl.connection.db_connection.jdbc_connection import JDBCTableExistBehavior
 
@@ -181,7 +180,8 @@ def test_jdbc_old_options_allowed_but_deprecated(arg, value):
     with pytest.warns(UserWarning, match=warning_msg):
         options = Postgres.Options.parse({arg: value})
 
-    assert options.dict(by_alias=True)[to_camel(arg)] == value
+    parsed_value = options.dict().get(arg) or options.dict(by_alias=True).get(arg)
+    assert parsed_value == value
 
 
 @pytest.mark.parametrize(