diff --git a/.github/workflows/run-tests.yml b/.github/workflows/run-tests.yml
index 3ecb74d..d6a6715 100644
--- a/.github/workflows/run-tests.yml
+++ b/.github/workflows/run-tests.yml
@@ -1,6 +1,6 @@
 name: Tests
 
-on: [push, pull_request]
+on: [ pull_request ]
 
 jobs:
   test:
@@ -8,11 +8,10 @@ jobs:
     strategy:
       fail-fast: true
       matrix:
-        os: [ubuntu-latest, windows-latest]
-        php: [7.4, 8.0]
-        dependency-version: [prefer-lowest, prefer-stable]
+        os: [ ubuntu-latest, windows-latest ]
+        php: [ 7.4, 8.0 ]
 
-    name: P${{ matrix.php }} - ${{ matrix.dependency-version }} - ${{ matrix.os }}
+    name: PHP ${{ matrix.php }} - ${{ matrix.os }}
 
     steps:
       - name: Checkout code
@@ -24,8 +23,16 @@ jobs:
           php-version: ${{ matrix.php }}
           coverage: none
 
+      - name: Cache composer dependencies
+        id: cache-run
+        uses: actions/cache@v2
+        with:
+          path: vendor
+          key: composer-${{ matrix.php }}-${{ matrix.os }}-${{ hashFiles('composer.lock') }}
+
       - name: Install dependencies
-        run: composer update --${{ matrix.dependency-version }} --prefer-dist --no-interaction
+        if: steps.cache-run.outputs.cache-hit != 'true'
+        run: composer update --prefer-dist --no-interaction
 
       - name: Execute tests
-        run: vendor/bin/pest
\ No newline at end of file
+        run: vendor/bin/pest
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 7469843..a91d77a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ## [Unreleased]
 ### Changed
 - Added `.gitattributes` to reduce disk usage.
+- Reimplemented using `IteratorAggregate` to improve performance.
 
 ## [1.0.1] - 2021-08-29
 ### Changed
diff --git a/composer.json b/composer.json
index 88be391..240f89d 100644
--- a/composer.json
+++ b/composer.json
@@ -17,6 +17,11 @@
             "src/iterator_functions.php"
         ]
     },
+    "autoload-dev": {
+        "psr-4": {
+            "DoekeNorg\\IteratorFunctions\\Tests\\": "tests"
+        }
+    },
     "license": "MIT",
     "authors": [
         {
diff --git a/src/Iterator/ColumnIterator.php b/src/Iterator/ColumnIterator.php
index ba2f8ef..1443c0a 100644
--- a/src/Iterator/ColumnIterator.php
+++ b/src/Iterator/ColumnIterator.php
@@ -5,7 +5,7 @@
 /**
  * Iterator that returns a single column for the iteration array / object.
  */
-class ColumnIterator extends \FilterIterator
+class ColumnIterator implements \IteratorAggregate
 {
     /**
      * The column to return.
@@ -25,6 +25,12 @@ class ColumnIterator extends \FilterIterator
      */
     private int $count = 0;
 
+    /**
+     * The inner iterator.
+     * @var \Traversable
+     */
+    private \Traversable $iterator;
+
     /**
      * Creates the iterator.
      * @param \Traversable $iterator The iterator that provides the arrays / objects.
@@ -33,76 +39,48 @@ class ColumnIterator extends \FilterIterator
      */
     public function __construct(\Traversable $iterator, $column_key, $index_key = null)
     {
-        parent::__construct($iterator);
-
+        $this->iterator = $iterator;
         $this->column_key = $column_key;
         $this->index_key = $index_key;
     }
 
-    /**
-     * @inheritdoc
-     */
-    public function next(): void
-    {
-        parent::next();
-
-        if (isset($this->index_key) && !$this->column($this->index_key)) {
-            ++$this->count;
-        }
-    }
-
-    /**
-     * @inheritdoc
-     */
-    public function key()
-    {
-        if (isset($this->index_key)) {
-            return $this->column($this->index_key) ?? $this->count;
-        }
-
-        return parent::key();
-    }
-
-    /**
-     * @inheritdoc
-     */
-    public function current()
-    {
-        if (isset($this->column_key)) {
-            return $this->column($this->column_key);
-        }
-
-        return parent::current();
-    }
-
     /**
      * Retrieves a single column from the current iteration.
+     * @param array|\ArrayAccess|object $iteration The iteration.
      * @param int|string $key The key to retrieve from the iteration.
-     * @return mixed|null The value.
+     * @return mixed The value.
      */
-    protected function column($key)
+    private function getColumn($iteration, $key)
     {
-        $iteration = parent::current();
         if (is_array($iteration) || $iteration instanceof \ArrayAccess) {
             return $iteration[$key] ?? null;
         }
 
         if (is_object($iteration)) {
-            return $iteration->{$key} ?? null;
+            return $iteration->{$key} ?: null;
         }
 
         return null;
     }
 
     /**
-     * @inheritdoc
+     * @inheritDoc
      */
-    public function accept(): bool
+    public function getIterator(): \Generator
     {
-        if (isset($this->column_key)) {
-            return $this->column($this->column_key) !== null;
+        foreach ($this->iterator as $key => $iteration) {
+            if (isset($this->index_key)) {
+                $key = $this->getColumn($iteration, $this->index_key) ?? $this->count++;
+            }
+
+            if (isset($this->column_key)) {
+                $iteration = $this->getColumn($iteration, $this->column_key);
+                if ($iteration === null) {
+                    continue;
+                }
+            }
+
+            yield $key => $iteration;
         }
-
-        return true;
     }
 }
diff --git a/src/Iterator/FlipIterator.php b/src/Iterator/FlipIterator.php
index e3ffb5f..f701ebc 100644
--- a/src/Iterator/FlipIterator.php
+++ b/src/Iterator/FlipIterator.php
@@ -5,21 +5,30 @@
 /**
  * Iterator that flips the key and the value of the current iteration.
  */
-class FlipIterator extends \IteratorIterator
+class FlipIterator implements \IteratorAggregate
 {
     /**
-     * @inheritdoc
+     * The inner iterator.
+     * @var \Traversable
      */
-    public function key()
+    private \Traversable $iterator;
+
+    /**
+     * Creates the iterator.
+     * @param \Traversable $iterator The inner iterator.
+     */
+    public function __construct(\Traversable $iterator)
     {
-        return parent::current();
+        $this->iterator = $iterator;
     }
 
     /**
-     * @inheritdoc
+     * @inheritDoc
      */
-    public function current()
+    public function getIterator(): \Generator
     {
-        return parent::key();
+        foreach ($this->iterator as $key => $value) {
+            yield $value => $key;
+        }
     }
 }
diff --git a/src/Iterator/KeysIterator.php b/src/Iterator/KeysIterator.php
index cbbab3e..ae41c60 100644
--- a/src/Iterator/KeysIterator.php
+++ b/src/Iterator/KeysIterator.php
@@ -5,14 +5,30 @@
 /**
  * Iterator that returns only the keys of the provided iterator.
  */
-class KeysIterator extends ValuesIterator
+class KeysIterator implements \IteratorAggregate
 {
     /**
-     * @inheritdoc
-     * @psalm-suppress UndefinedInterfaceMethod Psalm doesn't understand the inner iterator is an {@see \Iterator}.
+     * The inner iterator.
+     * @var \Traversable
      */
-    public function current()
+    private \Traversable $iterator;
+
+    /**
+     * Creates the iterator.
+     * @param \Traversable $iterator The inner iterator.
+     */
+    public function __construct(\Traversable $iterator)
+    {
+        $this->iterator = $iterator;
+    }
+
+    /**
+     * @inheritDoc
+     */
+    public function getIterator(): \Generator
     {
-        return $this->getInnerIterator()->key();
+        foreach ($this->iterator as $key => $_) {
+            yield $key;
+        }
     }
 }
diff --git a/src/Iterator/MapIterator.php b/src/Iterator/MapIterator.php
index 4815767..4194e8a 100644
--- a/src/Iterator/MapIterator.php
+++ b/src/Iterator/MapIterator.php
@@ -5,7 +5,7 @@
 /**
  * Iterator that applies a callback to the elements of the given iterators.
  */
-class MapIterator extends \IteratorIterator
+class MapIterator implements \IteratorAggregate
 {
     /**
      * Callback function to run for each element in each iterator.
@@ -13,6 +13,12 @@ class MapIterator extends \IteratorIterator
      */
     private $callback;
 
+    /**
+     * The inner iterator.
+     * @var \MultipleIterator
+     */
+    private \MultipleIterator $iterator;
+
     /**
      * Returns the iterator.
      * @param array|\Iterator ...$iterators Any iterator to apply the callback on. Can also be an array.
@@ -23,41 +29,31 @@ public function __construct(callable $callback, iterable ...$iterators)
         try {
             $function = new \ReflectionFunction(\Closure::fromCallable($callback));
         } catch (\ReflectionException $e) {
-            throw new \RuntimeException($e->getMessage(), (int) $e->getCode(), $e);
+            throw new \RuntimeException($e->getMessage(), (int)$e->getCode(), $e);
         }
 
         if (!$function->isVariadic() && $function->getNumberOfParameters() !== count($iterators)) {
             throw new \InvalidArgumentException('The callback needs as many arguments as provided iterators.');
         }
 
-        $inner = new \MultipleIterator();
+        $this->iterator = new \MultipleIterator();
         foreach ($iterators as $iterator) {
             if (is_array($iterator)) {
                 $iterator = new \ArrayIterator($iterator);
             }
-            $inner->attachIterator($iterator);
+            $this->iterator->attachIterator($iterator);
         }
 
-        parent::__construct($inner);
-
         $this->callback = $callback;
     }
 
     /**
-     * @inheritdoc
+     * @inheritDoc
      */
-    public function key()
+    public function getIterator(): \Generator
     {
-        $keys = parent::key();
-
-        return is_array($keys) ? reset($keys) : parent::key();
-    }
-
-    /**
-     * @inheritdoc
-     */
-    public function current()
-    {
-        return call_user_func_array($this->callback, parent::current());
+        foreach ($this->iterator as $key => $value) {
+            yield $key[0] => ($this->callback)(...$value);
+        }
     }
 }
diff --git a/src/Iterator/ValuesIterator.php b/src/Iterator/ValuesIterator.php
index e6b9740..265ddd7 100644
--- a/src/Iterator/ValuesIterator.php
+++ b/src/Iterator/ValuesIterator.php
@@ -5,44 +5,30 @@
 /**
  * Iterator that returns only the values of the provided iterator.
  */
-class ValuesIterator extends \IteratorIterator
+class ValuesIterator implements \IteratorAggregate
 {
     /**
-     * The internal key count.
-     * @var int
+     * The inner iterator.
+     * @var \Traversable
      */
-    private int $count = 0;
+    private \Traversable $iterator;
 
     /**
-     * @inheritdoc
+     * Creates the iterator.
+     * @param \Traversable $iterator The inner iterator.
      */
-    public function key(): int
+    public function __construct(\Traversable $iterator)
     {
-        return $this->count;
+        $this->iterator = $iterator;
     }
 
     /**
-     * @inheritdoc
-     *
-     * Increases the internal count.
-     *
+     * @inheritDoc
      */
-    public function next(): void
+    public function getIterator(): \Generator
     {
-        parent::next();
-        ++$this->count;
-    }
-
-    /**
-     * @inheritdoc
-     *
-     * Resets the internal count.
-     *
-     */
-    public function rewind(): void
-    {
-        parent::rewind();
-
-        $this->count = 0;
+        foreach ($this->iterator as $value) {
+            yield $value;
+        }
     }
 }