diff --git a/application/Espo/Core/Utils/Database/Helper.php b/application/Espo/Core/Utils/Database/Helper.php
index 1cb8c0f3f1..bc9ff7e0d4 100644
--- a/application/Espo/Core/Utils/Database/Helper.php
+++ b/application/Espo/Core/Utils/Database/Helper.php
@@ -30,7 +30,6 @@
 namespace Espo\Core\Utils\Database;
 
 use Espo\Core\{
-    Exceptions\Error,
     Utils\Config,
 };
 
@@ -51,11 +50,11 @@ use RuntimeException;
 
 class Helper
 {
-    private $config;
+    private ?Config $config;
 
-    private $dbalConnection;
+    private ?DbalConnection $dbalConnection = null;
 
-    private $pdoConnection;
+    private ?PDO $pdoConnection = null;
 
     private $driverPlatformMap = [
         'pdo_mysql' => 'Mysql',
@@ -79,7 +78,7 @@ class Helper
         $this->config = $config;
     }
 
-    public function getDbalConnection()
+    public function getDbalConnection(): DbalConnection
     {
         if (!isset($this->dbalConnection)) {
             $this->dbalConnection = $this->createDbalConnection();
@@ -88,7 +87,7 @@ class Helper
         return $this->dbalConnection;
     }
 
-    public function getPdoConnection()
+    public function getPdoConnection(): PDO
     {
         if (!isset($this->pdoConnection)) {
             $this->pdoConnection = $this->createPdoConnection();
@@ -97,17 +96,17 @@ class Helper
         return $this->pdoConnection;
     }
 
-    public function setDbalConnection(DbalConnection $dbalConnection)
+    public function setDbalConnection(DbalConnection $dbalConnection): void
     {
         $this->dbalConnection = $dbalConnection;
     }
 
-    public function setPdoConnection(PDO $pdoConnection)
+    public function setPdoConnection(PDO $pdoConnection): void
     {
         $this->pdoConnection = $pdoConnection;
     }
 
-    public function createDbalConnection(array $params = [])
+    public function createDbalConnection(array $params = []): DbalConnection
     {
         if (empty($params) && isset($this->config)) {
             $params = $this->config->get('database');
diff --git a/application/Espo/Core/Utils/Database/Schema/Schema.php b/application/Espo/Core/Utils/Database/Schema/Schema.php
index 0f21133835..bd03794959 100644
--- a/application/Espo/Core/Utils/Database/Schema/Schema.php
+++ b/application/Espo/Core/Utils/Database/Schema/Schema.php
@@ -33,6 +33,8 @@ use Doctrine\DBAL\{
     Types\Type,
     Schema\SchemaDiff as DBALSchemaDiff,
     Schema\Schema as DBALSchema,
+    Connection,
+    Platforms\AbstractPlatform,
 };
 
 use Espo\Core\{
@@ -54,38 +56,37 @@ use Throwable;
 
 class Schema
 {
-    private $config;
+    private Config $config;
 
-    private $metadata;
+    private Metadata $metadata;
 
-    private $fileManager;
+    private FileManager $fileManager;
 
-    private $entityManager;
+    private EntityManager $entityManager;
 
-    private $classMap;
+    private ClassMap $classMap;
 
-    private $comparator;
+    private Comparator $comparator;
 
-    private $converter;
+    private DatabaseConverter $converter;
 
-    private $databaseHelper;
+    private Helper $databaseHelper;
 
-    protected $ormMetadataData;
+    protected OrmMetadataData $ormMetadataData;
 
-    private $log;
+    private Log $log;
 
-    private $fieldTypePath = 'application/Espo/Core/Utils/Database/DBAL/FieldTypes';
+    private string $fieldTypePath = 'application/Espo/Core/Utils/Database/DBAL/FieldTypes';
 
-    private $rebuildActionsPath = 'Core/Utils/Database/Schema/rebuildActions';
+    private string $rebuildActionsPath = 'Core/Utils/Database/Schema/rebuildActions';
 
-    private $schemaConverter;
+    private Converter $schemaConverter;
 
     /**
-     * Array of rebuildActions classes in format:
-     * [
-     *   'beforeRebuild' => [...],
-     *   'afterRebuild' => [...],
-     * ]
+     * @var ?array{
+     *   beforeRebuild: \Espo\Core\Utils\Database\Schema\BaseRebuildActions[],
+     *   afterRebuild: \Espo\Core\Utils\Database\Schema\BaseRebuildActions[],
+     * }
      */
     protected $rebuildActionClasses = null;
 
@@ -107,7 +108,6 @@ class Schema
         $this->log = $log;
 
         $this->databaseHelper = new Helper($this->config);
-
         $this->comparator = new Comparator();
 
         $this->initFieldTypes();
@@ -126,54 +126,24 @@ class Schema
         $this->ormMetadataData = $ormMetadataData;
     }
 
-    protected function getConfig()
-    {
-        return $this->config;
-    }
-
-    protected function getMetadata()
-    {
-        return $this->metadata;
-    }
-
-    protected function getFileManager()
-    {
-        return $this->fileManager;
-    }
-
-    protected function getEntityManager()
-    {
-        return $this->entityManager;
-    }
-
-    protected function getComparator()
-    {
-        return $this->comparator;
-    }
-
-    protected function getConverter()
-    {
-        return $this->converter;
-    }
-
-    public function getPlatform()
-    {
-        return $this->getConnection()->getDatabasePlatform();
-    }
-
-    public function getDatabaseHelper()
+    public function getDatabaseHelper(): Helper
     {
         return $this->databaseHelper;
     }
 
-    public function getConnection()
+    public function getPlatform(): AbstractPlatform
+    {
+        return $this->getConnection()->getDatabasePlatform();
+    }
+
+    public function getConnection(): Connection
     {
         return $this->getDatabaseHelper()->getDbalConnection();
     }
 
-    protected function initFieldTypes()
+    protected function initFieldTypes(): void
     {
-        $typeList = $this->getFileManager()->getFileList($this->fieldTypePath, false, '\.php$');
+        $typeList = $this->fileManager->getFileList($this->fieldTypePath, false, '\.php$');
 
         foreach ($typeList as $name) {
             $typeName = preg_replace('/Type\.php$/i', '', $name);
@@ -197,12 +167,14 @@ class Schema
         }
     }
 
-    /*
+    /**
      * Rebuild database schema.
+     *
+     * @param ?string[] $entityList
      */
-    public function rebuild(?array $entityList = null) : bool
+    public function rebuild(?array $entityList = null): bool
     {
-        if (!$this->getConverter()->process()) {
+        if (!$this->converter->process()) {
             return false;
         }
 
@@ -251,34 +223,34 @@ class Schema
         return (bool) $result;
     }
 
-    /*
-    * Get current database schema.
-    *
-    * @return \Doctrine\DBAL\Schema\Schema
-    */
-    protected function getCurrentSchema()
+    /**
+     * Get current database schema.
+     */
+    protected function getCurrentSchema(): DBALSchema
     {
-        return $this->getConnection()->getSchemaManager()->createSchema();
+        return $this->getConnection()
+            ->getSchemaManager()
+            ->createSchema();
     }
 
-    /*
-    * Get SQL queries of database schema.
-    *
-    * @return array - array of SQL queries
-    */
+    /**
+     * Get SQL queries of database schema.
+     *
+     * @return string[] Array of SQL queries.
+     */
     public function toSql(DBALSchemaDiff $schema)
     {
         return $schema->toSaveSql($this->getPlatform());
     }
 
-    /*
-    * Get SQL queries to get from one to another schema.
-    *
-    * @return array - array of SQL queries.
-    */
+    /**
+     * Get SQL queries to get from one to another schema.
+     *
+     * @return string[] Array of SQL queries.
+     */
     public function getDiffSql(DBALSchema $fromSchema, DBALSchema $toSchema)
     {
-        $schemaDiff = $this->getComparator()->compare($fromSchema, $toSchema);
+        $schemaDiff = $this->comparator->compare($fromSchema, $toSchema);
 
         return $this->toSql($schemaDiff);
     }
@@ -286,13 +258,14 @@ class Schema
     /**
      * Init Rebuild Actions, get all classes and create them.
      */
-    protected function initRebuildActions($currentSchema = null, $metadataSchema = null)
+    protected function initRebuildActions(?DBALSchema $currentSchema = null, ?DBALSchema $metadataSchema = null): void
     {
         $methods = [
             'beforeRebuild',
             'afterRebuild',
         ];
 
+        /** @var array<string,class-string<\Espo\Core\Utils\Database\Schema\BaseRebuildActions>> */
         $rebuildActions = $this->classMap->getData($this->rebuildActionsPath, null, $methods);
 
         $classes = [];
@@ -326,18 +299,16 @@ class Schema
     /**
      * Execute actions for RebuildAction classes.
      *
-     * @param  string $action action name, possible values 'beforeRebuild' | 'afterRebuild'.
+     * @param string $action An action name, 'beforeRebuild' or 'afterRebuild'.
      */
-    protected function executeRebuildActions($action = 'beforeRebuild')
+    protected function executeRebuildActions(string $action = 'beforeRebuild'): void
     {
         if (!isset($this->rebuildActionClasses)) {
             $this->initRebuildActions();
         }
 
-        if (isset($this->rebuildActionClasses[$action])) {
-            foreach ($this->rebuildActionClasses[$action] as $rebuildActionClass) {
-                $rebuildActionClass->$action();
-            }
+        foreach ($this->rebuildActionClasses[$action] as $rebuildActionClass) {
+            $rebuildActionClass->$action();
         }
     }
 }
diff --git a/application/Espo/Core/Utils/Database/Schema/SchemaProxy.php b/application/Espo/Core/Utils/Database/Schema/SchemaProxy.php
index 1f4b68b47c..fe4fc02fe5 100644
--- a/application/Espo/Core/Utils/Database/Schema/SchemaProxy.php
+++ b/application/Espo/Core/Utils/Database/Schema/SchemaProxy.php
@@ -36,7 +36,7 @@ use Espo\Core\{
 
 class SchemaProxy
 {
-    private $container;
+    private Container $container;
 
     public function __construct(Container $container)
     {
@@ -48,12 +48,15 @@ class SchemaProxy
         return $this->container->get('schema');
     }
 
-    public function rebuild(?array $entityList = null) : bool
+    /**
+     * @param ?string[] $entityList
+     */
+    public function rebuild(?array $entityList = null): bool
     {
         return $this->getSchema()->rebuild();
     }
 
-    public function getDatabaseHelper() : Helper
+    public function getDatabaseHelper(): Helper
     {
         return $this->getSchema()->getDatabaseHelper();
     }
diff --git a/application/Espo/Core/Utils/Database/Schema/Utils.php b/application/Espo/Core/Utils/Database/Schema/Utils.php
index 6871b97192..0b51b487ea 100644
--- a/application/Espo/Core/Utils/Database/Schema/Utils.php
+++ b/application/Espo/Core/Utils/Database/Schema/Utils.php
@@ -33,6 +33,11 @@ use Espo\Core\Utils\Util;
 
 class Utils
 {
+    /**
+     * @param array<string,mixed> $ormMeta
+     * @param string[] $ignoreFlags
+     * @return array<string,array<string,mixed>>
+     */
     public static function getIndexes(array $ormMeta, array $ignoreFlags = [])
     {
         $indexList = [];
@@ -87,6 +92,10 @@ class Utils
         return $indexList;
     }
 
+    /**
+     * @param array<string,mixed> $fieldDefs
+     * @return ?string
+     */
     public static function getIndexTypeByFieldDefs(array $fieldDefs)
     {
         if ($fieldDefs['type'] != 'id' && isset($fieldDefs['unique']) && $fieldDefs['unique']) {
@@ -96,8 +105,16 @@ class Utils
         if (isset($fieldDefs['index']) && $fieldDefs['index']) {
             return 'index';
         }
+
+        return null;
     }
 
+    /**
+     * @param string $fieldName
+     * @param array<string,mixed> $fieldDefs
+     * @param mixed $default
+     * @return mixed
+     */
     public static function getIndexNameByFieldDefs($fieldName, array $fieldDefs, $default = null)
     {
         $indexType = static::getIndexTypeByFieldDefs($fieldDefs);
@@ -117,6 +134,11 @@ class Utils
         return $default;
     }
 
+    /**
+     * @param array<string,mixed> $fieldsDefs
+     * @param bool $isTableColumnNames
+     * @return array<string,mixed>
+     */
     public static function getEntityIndexListByFieldsDefs(array $fieldsDefs, $isTableColumnNames = false)
     {
         $indexList = [];
@@ -150,6 +172,10 @@ class Utils
         return $indexList;
     }
 
+    /**
+     * @param array<string,mixed> $indexDefs
+     * @return string
+     */
     public static function getIndexTypeByIndexDefs(array $indexDefs)
     {
         if (
@@ -166,6 +192,12 @@ class Utils
         return 'index';
     }
 
+    /**
+     * @param string $name
+     * @param string $type
+     * @param int $maxLength
+     * @return string
+     */
     public static function generateIndexName($name, $type = 'index', $maxLength = 60)
     {
         switch ($type) {
@@ -185,6 +217,14 @@ class Utils
         return substr(implode('_', $nameList), 0, $maxLength);
     }
 
+    /**
+     *
+     * @param array<string,mixed> $ormMeta
+     * @param int $indexMaxLength
+     * @param ?array<string,mixed> $indexList
+     * @param int $characterLength
+     * @return array<string,mixed>
+     */
     public static function getFieldListExceededIndexMaxLength(
         array $ormMeta,
         $indexMaxLength = 1000,
@@ -244,6 +284,11 @@ class Utils
         return $fields;
     }
 
+    /**
+     * @param array<string,mixed> $ormFieldDefs
+     * @param int $characterLength
+     * @return int
+     */
     protected static function getFieldLength(array $ormFieldDefs, $characterLength = 4)
     {
         $length = 0;
@@ -264,7 +309,7 @@ class Utils
         $type = static::getDbFieldType($ormFieldDefs);
 
         $length = isset($defaultLength[$type]) ? $defaultLength[$type] : $length;
-        $length = isset($ormFieldDefs['len']) ? $ormFieldDefs['len'] : $length;
+        //$length = isset($ormFieldDefs['len']) ? $ormFieldDefs['len'] : $length;
 
         switch ($type) {
             case 'varchar':
@@ -275,11 +320,19 @@ class Utils
         return $length;
     }
 
+    /**
+     * @param array<string,mixed> $ormFieldDefs
+     * @return string
+     */
     protected static function getDbFieldType(array $ormFieldDefs)
     {
         return isset($ormFieldDefs['dbType']) ? $ormFieldDefs['dbType'] : $ormFieldDefs['type'];
     }
 
+    /**
+     * @param array<string,mixed> $ormFieldDefs
+     * @return string
+     */
     protected static function getFieldType(array $ormFieldDefs)
     {
         return isset($ormFieldDefs['type']) ? $ormFieldDefs['type'] : static::getDbFieldType($ormFieldDefs);
diff --git a/application/Espo/Core/Utils/Database/Schema/rebuildActions/AddSystemUser.php b/application/Espo/Core/Utils/Database/Schema/rebuildActions/AddSystemUser.php
index 60068deb4a..f06d5e9a39 100644
--- a/application/Espo/Core/Utils/Database/Schema/rebuildActions/AddSystemUser.php
+++ b/application/Espo/Core/Utils/Database/Schema/rebuildActions/AddSystemUser.php
@@ -33,6 +33,9 @@ use Espo\Core\Utils\Database\Schema\BaseRebuildActions as Base;
 
 class AddSystemUser extends Base
 {
+    /**
+     * @return void
+     */
     public function afterRebuild()
     {
         $userId = $this->getConfig()->get('systemUserAttributes.id');
diff --git a/application/Espo/Core/Utils/Database/Schema/rebuildActions/Currency.php b/application/Espo/Core/Utils/Database/Schema/rebuildActions/Currency.php
index 82d3e1528b..11bfd65565 100644
--- a/application/Espo/Core/Utils/Database/Schema/rebuildActions/Currency.php
+++ b/application/Espo/Core/Utils/Database/Schema/rebuildActions/Currency.php
@@ -33,6 +33,9 @@ use Espo\Core\Utils\Currency\DatabasePopulator;
 
 class Currency extends \Espo\Core\Utils\Database\Schema\BaseRebuildActions
 {
+    /**
+     * @return void
+     */
     public function afterRebuild()
     {
         $populator = new DatabasePopulator($this->getConfig(), $this->getEntityManager());
diff --git a/application/Espo/Core/Utils/Database/Schema/rebuildActions/FulltextIndex.php b/application/Espo/Core/Utils/Database/Schema/rebuildActions/FulltextIndex.php
index 5f4847339e..8679b9ba47 100644
--- a/application/Espo/Core/Utils/Database/Schema/rebuildActions/FulltextIndex.php
+++ b/application/Espo/Core/Utils/Database/Schema/rebuildActions/FulltextIndex.php
@@ -36,6 +36,9 @@ use Exception;
 
 class FulltextIndex extends BaseRebuildActions
 {
+    /**
+     * @return void
+     */
     public function beforeRebuild()
     {
         $currentSchema = $this->getCurrentSchema();
diff --git a/application/Espo/Core/Utils/File/ClassMap.php b/application/Espo/Core/Utils/File/ClassMap.php
index 10ef0f6bc3..8a490be3d0 100644
--- a/application/Espo/Core/Utils/File/ClassMap.php
+++ b/application/Espo/Core/Utils/File/ClassMap.php
@@ -75,7 +75,7 @@ class ClassMap
      * Return paths to class files.
      *
      * @param ?string[] $allowedMethods If specified, classes w/o specified method will be ignored.
-     * @return array<string,string>
+     * @return array<string,class-string>
      */
     public function getData(
         string $path,
@@ -138,7 +138,7 @@ class ClassMap
     /**
      * @param string[]|string $dirs
      * @param ?string[] $allowedMethods
-     * @return array<string,string>
+     * @return array<string,class-string>
      */
     private function getClassNameHash($dirs, ?array $allowedMethods = [], bool $subDirs = false): array
     {
@@ -162,7 +162,7 @@ class ClassMap
     /**
      * @param string[] $fileList
      * @param ?string[] $allowedMethods
-     * @param array<string,string> $data
+     * @param array<string,class-string> $data
      */
     private function fillHashFromFileList(
         array $fileList,