diff --git a/src/adapter/etl-adapter-doctrine/src/Flow/ETL/Adapter/Doctrine/DbalLoader.php b/src/adapter/etl-adapter-doctrine/src/Flow/ETL/Adapter/Doctrine/DbalLoader.php
index 7598893eb..bed468934 100644
--- a/src/adapter/etl-adapter-doctrine/src/Flow/ETL/Adapter/Doctrine/DbalLoader.php
+++ b/src/adapter/etl-adapter-doctrine/src/Flow/ETL/Adapter/Doctrine/DbalLoader.php
@@ -16,7 +16,7 @@
 /**
  * @implements Loader<array{
  *  table_name: string,
- *  chunk_size: int,
+ *  chunk_size: int<1, max>,
  *  connection_params: array<string, mixed>,
  *  operation: string,
  *  operation_options: array{
@@ -35,8 +35,7 @@ final class DbalLoader implements Loader
     private string $operation;
 
     /**
-     * @param string $tableName
-     * @param int $chunkSize
+     * @param int<1, max> $chunkSize
      * @param array<string, mixed> $connectionParams
      * @param array{
      *  skip_conflicts?: boolean,
@@ -45,7 +44,6 @@ final class DbalLoader implements Loader
      *  update_columns?: array<string>,
      *  primary_key_columns?: array<string>
      * } $operationOptions
-     * @param string $operation
      *
      * @throws InvalidArgumentException
      */
@@ -66,9 +64,7 @@ public function __construct(
      * Since Connection::getParams() is marked as an internal method, please
      * use this constructor with caution.
      *
-     * @param Connection $connection
-     * @param string $tableName
-     * @param int $chunkSize
+     * @param int<1, max> $chunkSize
      * @param array{
      *  skip_conflicts?: boolean,
      *  constraint?: string,
@@ -76,7 +72,6 @@ public function __construct(
      *  update_columns?: array<string>,
      *  primary_key_columns?: array<string>
      * } $operationOptions
-     * @param string $operation
      *
      * @throws InvalidArgumentException
      */
diff --git a/src/adapter/etl-adapter-doctrine/src/Flow/ETL/DSL/Dbal.php b/src/adapter/etl-adapter-doctrine/src/Flow/ETL/DSL/Dbal.php
index 988ee4a26..07731e9f3 100644
--- a/src/adapter/etl-adapter-doctrine/src/Flow/ETL/DSL/Dbal.php
+++ b/src/adapter/etl-adapter-doctrine/src/Flow/ETL/DSL/Dbal.php
@@ -71,8 +71,6 @@ final public static function from_limit_offset(
      * @param int $page_size
      * @param null|int $maximum
      *
-     * @throws InvalidArgumentException
-     *
      * @return Extractor
      */
     final public static function from_limit_offset_qb(
@@ -135,8 +133,7 @@ final public static function from_query(
 
     /**
      * @param array<string, mixed>|Connection $connection
-     * @param string $table
-     * @param int $chunk_size
+     * @param int<1, max> $chunk_size
      * @param array{
      *  skip_conflicts?: boolean,
      *  constraint?: string,
@@ -146,8 +143,6 @@ final public static function from_query(
      * } $options
      *
      * @throws InvalidArgumentException
-     *
-     * @return Loader
      */
     final public static function to_table_insert(
         array|Connection $connection,
@@ -162,8 +157,7 @@ final public static function to_table_insert(
 
     /**
      * @param array<string, mixed>|Connection $connection
-     * @param string $table
-     * @param int $chunk_size
+     * @param int<1, max> $chunk_size
      * @param array{
      *  skip_conflicts?: boolean,
      *  constraint?: string,
diff --git a/src/adapter/etl-adapter-elasticsearch/src/Flow/ETL/Adapter/Elasticsearch/ElasticsearchPHP/ElasticsearchLoader.php b/src/adapter/etl-adapter-elasticsearch/src/Flow/ETL/Adapter/Elasticsearch/ElasticsearchPHP/ElasticsearchLoader.php
index e34b4cc28..33528f3a7 100644
--- a/src/adapter/etl-adapter-elasticsearch/src/Flow/ETL/Adapter/Elasticsearch/ElasticsearchPHP/ElasticsearchLoader.php
+++ b/src/adapter/etl-adapter-elasticsearch/src/Flow/ETL/Adapter/Elasticsearch/ElasticsearchPHP/ElasticsearchLoader.php
@@ -25,7 +25,7 @@
  *    elasticMetaHeader?: boolean,
  *    includePortInHostHeader?: boolean
  *  },
- *  chunk_size: int,
+ *  chunk_size: int<1, max>,
  *  index: string,
  *  id_factory: IdFactory,
  *  parameters: array<mixed>,
@@ -41,6 +41,7 @@ final class ElasticsearchLoader implements Loader
 
     /**
      * @param array{hosts?: array<string>, connectionParams?: array<mixed>, retries?: int, sniffOnStart?: boolean, sslCert?: array<string>, sslKey?: array<string>, sslVerification?: (boolean|string), elasticMetaHeader?: boolean, includePortInHostHeader?: boolean} $config
+     * @param int<1, max> $chunkSize
      * @param array<mixed> $parameters
      */
     public function __construct(
@@ -66,6 +67,7 @@ public function __construct(
      *  elasticMetaHeader?: boolean,
      *  includePortInHostHeader?: boolean
      * } $clientConfig
+     * @param int<1, max> $chunkSize
      * @param array<mixed> $parameters
      */
     public static function update(array $clientConfig, int $chunkSize, string $index, IdFactory $idFactory, array $parameters = []) : self
diff --git a/src/adapter/etl-adapter-elasticsearch/src/Flow/ETL/DSL/Elasticsearch.php b/src/adapter/etl-adapter-elasticsearch/src/Flow/ETL/DSL/Elasticsearch.php
index 4d9350cf9..af98f6b86 100644
--- a/src/adapter/etl-adapter-elasticsearch/src/Flow/ETL/DSL/Elasticsearch.php
+++ b/src/adapter/etl-adapter-elasticsearch/src/Flow/ETL/DSL/Elasticsearch.php
@@ -29,7 +29,7 @@ class Elasticsearch
      *  elasticMetaHeader?: boolean,
      *  includePortInHostHeader?: boolean
      * } $config
-     * @param int $chunk_size
+     * @param int<1, max> $chunk_size
      * @param string $index
      * @param IdFactory $id_factory
      * @param array<mixed> $parameters - https://www.elastic.co/guide/en/elasticsearch/reference/master/docs-bulk.html
@@ -60,7 +60,7 @@ final public static function bulk_index(
      *  elasticMetaHeader?: boolean,
      *  includePortInHostHeader?: boolean
      * } $config
-     * @param int $chunk_size
+     * @param int<1, max> $chunk_size
      * @param string $index
      * @param IdFactory $id_factory
      * @param array<mixed> $parameters - https://www.elastic.co/guide/en/elasticsearch/reference/master/docs-bulk.html
diff --git a/src/core/etl/src/Flow/ETL/DSL/From.php b/src/core/etl/src/Flow/ETL/DSL/From.php
index 253e55237..173f8769a 100644
--- a/src/core/etl/src/Flow/ETL/DSL/From.php
+++ b/src/core/etl/src/Flow/ETL/DSL/From.php
@@ -35,6 +35,9 @@ final public static function array(array $array, int $batch_size = 100) : Extrac
         return new MemoryExtractor(new ArrayMemory($array), $batch_size);
     }
 
+    /**
+     * @param int<1, max> $max_row_size
+     */
     final public static function buffer(Extractor $extractor, int $max_row_size) : Extractor
     {
         return new Extractor\BufferExtractor($extractor, $max_row_size);
@@ -50,6 +53,9 @@ final public static function chain(Extractor ...$extractors) : Extractor
         return new Extractor\ChainExtractor(...$extractors);
     }
 
+    /**
+     * @param int<1, max> $chunk_size
+     */
     final public static function chunks_from(Extractor $extractor, int $chunk_size) : Extractor
     {
         return new Extractor\ChunkExtractor($extractor, $chunk_size);
diff --git a/src/core/etl/src/Flow/ETL/DSL/To.php b/src/core/etl/src/Flow/ETL/DSL/To.php
index 1f908ea5f..68c59d4e8 100644
--- a/src/core/etl/src/Flow/ETL/DSL/To.php
+++ b/src/core/etl/src/Flow/ETL/DSL/To.php
@@ -18,6 +18,9 @@
  */
 class To
 {
+    /**
+     * @param int<1, max> $bufferSize
+     */
     final public static function buffer(Loader $overflowLoader, int $bufferSize) : Loader
     {
         return new Loader\BufferLoader($overflowLoader, $bufferSize);
diff --git a/src/core/etl/src/Flow/ETL/DataFrame.php b/src/core/etl/src/Flow/ETL/DataFrame.php
index c8137fc2c..4ec766908 100644
--- a/src/core/etl/src/Flow/ETL/DataFrame.php
+++ b/src/core/etl/src/Flow/ETL/DataFrame.php
@@ -416,7 +416,7 @@ public function onError(ErrorHandler $handler) : self
      *
      * @lazy
      *
-     * @throws InvalidArgumentException
+     * @param int<1, max> $chunks
      */
     public function parallelize(int $chunks) : self
     {
diff --git a/src/core/etl/src/Flow/ETL/ExternalSort/BufferCache.php b/src/core/etl/src/Flow/ETL/ExternalSort/BufferCache.php
index 4bde76c54..633dd60ee 100644
--- a/src/core/etl/src/Flow/ETL/ExternalSort/BufferCache.php
+++ b/src/core/etl/src/Flow/ETL/ExternalSort/BufferCache.php
@@ -17,6 +17,9 @@ final class BufferCache
      */
     private array $buffers = [];
 
+    /**
+     * @param int<1, max> $bufferSize
+     */
     public function __construct(
         private readonly Cache $overflowCache,
         private readonly int $bufferSize
diff --git a/src/core/etl/src/Flow/ETL/ExternalSort/CacheExternalSort.php b/src/core/etl/src/Flow/ETL/ExternalSort/CacheExternalSort.php
index 9a6e123a7..9fa7f4c5c 100644
--- a/src/core/etl/src/Flow/ETL/ExternalSort/CacheExternalSort.php
+++ b/src/core/etl/src/Flow/ETL/ExternalSort/CacheExternalSort.php
@@ -34,7 +34,7 @@ public function sortBy(EntryReference ...$refs) : Extractor
     {
         /** @var array<string, \Generator<Rows>> $cachedPartsArray */
         $cachedPartsArray = [];
-        $maxRowsSize = 0;
+        $maxRowsSize = 1;
 
         /** @var int $i */
         foreach ($this->cache->read($this->id) as $i => $rows) {
diff --git a/src/core/etl/src/Flow/ETL/ExternalSort/MemorySort.php b/src/core/etl/src/Flow/ETL/ExternalSort/MemorySort.php
index 11d946f0a..cd7b6500c 100644
--- a/src/core/etl/src/Flow/ETL/ExternalSort/MemorySort.php
+++ b/src/core/etl/src/Flow/ETL/ExternalSort/MemorySort.php
@@ -31,7 +31,7 @@ public function __construct(
         private readonly Cache $cache,
         private Unit $maximumMemory
     ) {
-        $this->configuration = new Configuration($safetyBufferPercentage = 10);
+        $this->configuration = new Configuration(10);
 
         if ($this->configuration->isLessThan($maximumMemory) && !$this->configuration->isInfinite()) {
             /**
@@ -48,7 +48,7 @@ public function sortBy(EntryReference ...$refs) : Extractor
         $memoryConsumption = new Consumption();
 
         $mergedRows = new Rows();
-        $maxSize = 0;
+        $maxSize = 1;
 
         foreach ($this->cache->read($this->cacheId) as $rows) {
             $maxSize = \max($rows->count(), $maxSize);
@@ -64,6 +64,6 @@ public function sortBy(EntryReference ...$refs) : Extractor
 
         $this->cache->clear($this->cacheId);
 
-        return new Extractor\ProcessExtractor(...$mergedRows->sortBy(...$refs)->chunks($maxSize));
+        return new Extractor\ProcessExtractor(...\iterator_to_array($mergedRows->sortBy(...$refs)->chunks($maxSize)));
     }
 }
diff --git a/src/core/etl/src/Flow/ETL/Extractor/BufferExtractor.php b/src/core/etl/src/Flow/ETL/Extractor/BufferExtractor.php
index 6b21697ba..aca0c9f72 100644
--- a/src/core/etl/src/Flow/ETL/Extractor/BufferExtractor.php
+++ b/src/core/etl/src/Flow/ETL/Extractor/BufferExtractor.php
@@ -10,6 +10,9 @@
 
 final class BufferExtractor implements Extractor, OverridingExtractor
 {
+    /**
+     * @param int<1, max> $maxRowsSize
+     */
     public function __construct(
         private readonly Extractor $extractor,
         private readonly int $maxRowsSize
diff --git a/src/core/etl/src/Flow/ETL/Extractor/ChunkExtractor.php b/src/core/etl/src/Flow/ETL/Extractor/ChunkExtractor.php
index ce8ea4fb7..c2407356e 100644
--- a/src/core/etl/src/Flow/ETL/Extractor/ChunkExtractor.php
+++ b/src/core/etl/src/Flow/ETL/Extractor/ChunkExtractor.php
@@ -9,6 +9,9 @@
 
 final class ChunkExtractor implements Extractor, OverridingExtractor
 {
+    /**
+     * @param int<1, max> $chunkSize
+     */
     public function __construct(
         private readonly Extractor $extractor,
         private readonly int $chunkSize
diff --git a/src/core/etl/src/Flow/ETL/Loader/BufferLoader.php b/src/core/etl/src/Flow/ETL/Loader/BufferLoader.php
index 1cc1d53c5..fc86eb94c 100644
--- a/src/core/etl/src/Flow/ETL/Loader/BufferLoader.php
+++ b/src/core/etl/src/Flow/ETL/Loader/BufferLoader.php
@@ -10,12 +10,15 @@
 use Flow\ETL\Rows;
 
 /**
- * @implements Loader<array{overflow_loader: Loader, buffer_size: int}>
+ * @implements Loader<array{overflow_loader: Loader, buffer_size: int<1, max>}>
  */
 final class BufferLoader implements Closure, Loader, OverridingLoader
 {
     private Rows $buffer;
 
+    /**
+     * @param int<1, max> $bufferSize
+     */
     public function __construct(private readonly Loader $overflowLoader, private readonly int $bufferSize)
     {
         $this->buffer = new Rows();
diff --git a/src/core/etl/src/Flow/ETL/Pipeline/ParallelizingPipeline.php b/src/core/etl/src/Flow/ETL/Pipeline/ParallelizingPipeline.php
index 7dc38a1f0..aea050821 100644
--- a/src/core/etl/src/Flow/ETL/Pipeline/ParallelizingPipeline.php
+++ b/src/core/etl/src/Flow/ETL/Pipeline/ParallelizingPipeline.php
@@ -5,7 +5,6 @@
 namespace Flow\ETL\Pipeline;
 
 use Flow\ETL\DSL\From;
-use Flow\ETL\Exception\InvalidArgumentException;
 use Flow\ETL\Extractor;
 use Flow\ETL\FlowContext;
 use Flow\ETL\Loader;
@@ -20,14 +19,13 @@ final class ParallelizingPipeline implements Pipeline
 {
     private readonly Pipeline $nextPipeline;
 
+    /**
+     * @param int<1, max> $parallel
+     */
     public function __construct(
         private readonly Pipeline $pipeline,
         private readonly int $parallel
     ) {
-        if ($parallel < 1) {
-            throw new InvalidArgumentException("Parallel value can't be lower than 1.");
-        }
-
         $this->nextPipeline = $pipeline->cleanCopy();
     }
 
diff --git a/src/core/etl/src/Flow/ETL/Rows.php b/src/core/etl/src/Flow/ETL/Rows.php
index 6aa406118..8d912619e 100644
--- a/src/core/etl/src/Flow/ETL/Rows.php
+++ b/src/core/etl/src/Flow/ETL/Rows.php
@@ -59,26 +59,21 @@ public function __unserialize(array $data) : void
     public function add(Row ...$rows) : self
     {
         return new self(
-            ...\array_merge($this->rows, $rows)
+            ...$this->rows,
+            ...$rows
         );
     }
 
     /**
-     * @return Rows[]
+     * @param int<1, max> $size
+     *
+     * @return \Generator<Rows>
      */
-    public function chunks(int $size) : array
+    public function chunks(int $size) : \Generator
     {
-        if ($size < 1) {
-            throw InvalidArgumentException::because('Chunk size must be greater than 0');
-        }
-
-        $chunks = [];
-
         foreach (\array_chunk($this->rows, $size) as $chunk) {
-            $chunks[] = new self(...$chunk);
+            yield new self(...$chunk);
         }
-
-        return $chunks;
     }
 
     public function count() : int
diff --git a/src/core/etl/tests/Flow/ETL/Tests/Unit/RowsTest.php b/src/core/etl/tests/Flow/ETL/Tests/Unit/RowsTest.php
index 518c582ba..24b1afbfd 100644
--- a/src/core/etl/tests/Flow/ETL/Tests/Unit/RowsTest.php
+++ b/src/core/etl/tests/Flow/ETL/Tests/Unit/RowsTest.php
@@ -189,13 +189,6 @@ public function test_building_rows_from_array() : void
         );
     }
 
-    public function test_chunks_smaller_than_1() : void
-    {
-        $this->expectException(InvalidArgumentException::class);
-
-        (new Rows())->chunks(-1);
-    }
-
     public function test_chunks_with_less() : void
     {
         $rows = new Rows(
@@ -208,8 +201,10 @@ public function test_chunks_with_less() : void
             Row::create(new IntegerEntry('id', 7)),
         );
 
-        $this->assertCount(1, $rows->chunks(10));
-        $this->assertSame([1, 2, 3, 4, 5, 6, 7], $rows->chunks(10)[0]->reduceToArray('id'));
+        $chunk = \iterator_to_array($rows->chunks(10));
+
+        $this->assertCount(1, $chunk);
+        $this->assertSame([1, 2, 3, 4, 5, 6, 7], $chunk[0]->reduceToArray('id'));
     }
 
     public function test_chunks_with_more_than_expected_in_chunk_rows() : void
@@ -227,9 +222,11 @@ public function test_chunks_with_more_than_expected_in_chunk_rows() : void
             Row::create(new IntegerEntry('id', 10)),
         );
 
-        $this->assertCount(2, $rows->chunks(5));
-        $this->assertSame([1, 2, 3, 4, 5], $rows->chunks(5)[0]->reduceToArray('id'));
-        $this->assertSame([6, 7, 8, 9, 10], $rows->chunks(5)[1]->reduceToArray('id'));
+        $chunk = \iterator_to_array($rows->chunks(5));
+
+        $this->assertCount(2, $chunk);
+        $this->assertSame([1, 2, 3, 4, 5], $chunk[0]->reduceToArray('id'));
+        $this->assertSame([6, 7, 8, 9, 10], $chunk[1]->reduceToArray('id'));
     }
 
     public function test_drop() : void