diff --git a/src/Contracts/Application/Command.php b/src/Contracts/Application/Command.php
new file mode 100644
index 0000000..1f4b222
--- /dev/null
+++ b/src/Contracts/Application/Command.php
@@ -0,0 +1,9 @@
+<?php
+
+declare(strict_types=1);
+
+namespace GeekCell\Ddd\Contracts\Application;
+
+interface Command
+{
+}
diff --git a/src/Contracts/Application/CommandBus.php b/src/Contracts/Application/CommandBus.php
new file mode 100644
index 0000000..2fe289a
--- /dev/null
+++ b/src/Contracts/Application/CommandBus.php
@@ -0,0 +1,16 @@
+<?php
+
+declare(strict_types=1);
+
+namespace GeekCell\Ddd\Contracts\Application;
+
+interface CommandBus
+{
+    /**
+     * Dispatch a command to the appropriate handler.
+     *
+     * @param Command $command
+     * @return mixed
+     */
+    public function dispatch(Command $command): mixed;
+}
diff --git a/src/Contracts/Application/CommandHandler.php b/src/Contracts/Application/CommandHandler.php
new file mode 100644
index 0000000..a3cfc58
--- /dev/null
+++ b/src/Contracts/Application/CommandHandler.php
@@ -0,0 +1,18 @@
+<?php
+
+declare(strict_types=1);
+
+namespace GeekCell\Ddd\Contracts\Application;
+
+use GeekCell\Ddd\Contracts\Core\Interactable;
+
+interface CommandHandler extends Interactable
+{
+    /**
+     * Execute a command.
+     *
+     * @param Command $command
+     * @return mixed
+     */
+    public function execute(Command $command): mixed;
+}
diff --git a/src/Contracts/Application/Query.php b/src/Contracts/Application/Query.php
new file mode 100644
index 0000000..8e2e7d0
--- /dev/null
+++ b/src/Contracts/Application/Query.php
@@ -0,0 +1,9 @@
+<?php
+
+declare(strict_types=1);
+
+namespace GeekCell\Ddd\Contracts\Application;
+
+interface Query
+{
+}
diff --git a/src/Contracts/Application/QueryBus.php b/src/Contracts/Application/QueryBus.php
new file mode 100644
index 0000000..a2bc25c
--- /dev/null
+++ b/src/Contracts/Application/QueryBus.php
@@ -0,0 +1,16 @@
+<?php
+
+declare(strict_types=1);
+
+namespace GeekCell\Ddd\Contracts\Application;
+
+interface QueryBus
+{
+    /**
+     * Dispatch a query to the appropriate handler.
+     *
+     * @param Query $query
+     * @return mixed
+     */
+    public function dispatch(Query $query): mixed;
+}
diff --git a/src/Contracts/Application/QueryHandler.php b/src/Contracts/Application/QueryHandler.php
new file mode 100644
index 0000000..4218c76
--- /dev/null
+++ b/src/Contracts/Application/QueryHandler.php
@@ -0,0 +1,18 @@
+<?php
+
+declare(strict_types=1);
+
+namespace GeekCell\Ddd\Contracts\Application;
+
+use GeekCell\Ddd\Contracts\Core\Interactable;
+
+interface QueryHandler extends Interactable
+{
+    /**
+     * Execute a query.
+     *
+     * @param Query $query
+     * @return mixed
+     */
+    public function execute(Query $query): mixed;
+}
diff --git a/src/Contracts/Core/Interactable.php b/src/Contracts/Core/Interactable.php
new file mode 100644
index 0000000..4a5b71a
--- /dev/null
+++ b/src/Contracts/Core/Interactable.php
@@ -0,0 +1,9 @@
+<?php
+
+declare(strict_types=1);
+
+namespace GeekCell\Ddd\Contracts\Core;
+
+interface Interactable
+{
+}
diff --git a/src/Infrastructure/InMemory/AbstractBus.php b/src/Infrastructure/InMemory/AbstractBus.php
new file mode 100644
index 0000000..30a9ed0
--- /dev/null
+++ b/src/Infrastructure/InMemory/AbstractBus.php
@@ -0,0 +1,98 @@
+<?php
+
+declare(strict_types=1);
+
+namespace GeekCell\Ddd\Infrastructure\InMemory;
+
+use GeekCell\Ddd\Contracts\Core\Interactable;
+use GeekCell\Ddd\Support\Attributes\ForType;
+
+abstract class AbstractBus
+{
+    /**
+     * @var array<string, mixed>
+     */
+    protected array $handlers = [];
+
+    /**
+     * @return array<string, mixed>
+     */
+    public function getHandlers(): array
+    {
+        return $this->handlers;
+    }
+
+    /**
+     * Register a handler.
+     *
+     * The handler can be a callable or an object that implements
+     * the Interactable interface and has the ForType class attribute.
+     *
+     * @param mixed $handler
+     * @return void
+     */
+    abstract public function registerHandler(mixed $handler): void;
+
+    /**
+     * Register a callable handler.
+     *
+     * @param callable $callable     The callable to register
+     * @param string $parameterType  The type of the parameter that the callable
+     *
+     * @return void
+     */
+    protected function registerCallableHandler(
+        callable $callable,
+        string $parameterType,
+    ): void
+    {
+        $reflectionMethod = new \ReflectionMethod($callable, '__invoke');
+        foreach ($reflectionMethod->getParameters() as $parameter) {
+            $type = $parameter->getType();
+            if (
+                is_subclass_of($type->getName(), $parameterType) &&
+                $type->allowsNull() === false) {
+                $this->handlers[$type->getName()] = $callable;
+            }
+        }
+    }
+
+    /**
+     * Register a handler class.
+     *
+     * @param Interactable $handler  The handler to register
+     * @param string $attributeType  Class attribute which is a
+     *                               subclass of ForType
+     * @return void
+     */
+    protected function registerHandlerClass(
+        Interactable $handler,
+        string $attributeType,
+    ): void
+    {
+        $reflectionClass = new \ReflectionClass($handler);
+        $attributes = $reflectionClass->getAttributes();
+        foreach ($attributes as $attribute) {
+            if (
+                is_subclass_of($attributeType, ForType::class) &&
+                $attribute->getName() !== $attributeType) {
+                continue;
+            }
+
+            /** @var ForType $context */
+            $context = $attribute->newInstance();
+            if (!$context->isValid()) {
+                return;
+            }
+
+            foreach ($reflectionClass->getMethods() as $method) {
+                if ($method->getName() === $context->getHandler()) {
+                    $this->handlers[$context->getType()] = [
+                        $handler,
+                        $method->getName()
+                    ];
+                }
+            }
+        }
+    }
+}
diff --git a/src/Infrastructure/InMemory/CommandBus.php b/src/Infrastructure/InMemory/CommandBus.php
new file mode 100644
index 0000000..3fece0c
--- /dev/null
+++ b/src/Infrastructure/InMemory/CommandBus.php
@@ -0,0 +1,49 @@
+<?php
+
+declare(strict_types=1);
+
+namespace GeekCell\Ddd\Infrastructure\InMemory;
+
+use GeekCell\Ddd\Contracts\Application\Command;
+use GeekCell\Ddd\Contracts\Application\CommandBus as CommandBusInterface;
+use GeekCell\Ddd\Contracts\Application\CommandHandler;
+use GeekCell\Ddd\Support\Attributes\For\Command as ForCommand;
+
+class CommandBus extends AbstractBus implements CommandBusInterface
+{
+    /**
+     * @inheritDoc
+     */
+    public function dispatch(Command $command): mixed
+    {
+        $commandType = get_class($command);
+        if (!array_key_exists($commandType, $this->handlers)) {
+            return null;
+        }
+
+        $handler = $this->handlers[$commandType];
+        if (is_callable($handler)) {
+            return $handler($command);
+        }
+
+        if (is_array($handler)) {
+            [$handler, $method] = $handler;
+            return call_user_func([$handler, $method], $command);
+        }
+    }
+
+    /**
+     * @inheritDoc
+     */
+    public function registerHandler(mixed $handler): void
+    {
+        if (is_callable($handler)) {
+            $this->registerCallableHandler($handler, Command::class);
+            return;
+        }
+
+        if ($handler instanceof CommandHandler) {
+            $this->registerHandlerClass($handler, ForCommand::class);
+        }
+    }
+}
diff --git a/src/Infrastructure/InMemoryPaginator.php b/src/Infrastructure/InMemory/Paginator.php
similarity index 90%
rename from src/Infrastructure/InMemoryPaginator.php
rename to src/Infrastructure/InMemory/Paginator.php
index bfd4b27..31b0f84 100644
--- a/src/Infrastructure/InMemoryPaginator.php
+++ b/src/Infrastructure/InMemory/Paginator.php
@@ -2,15 +2,15 @@
 
 declare(strict_types=1);
 
-namespace GeekCell\Ddd\Infrastructure;
+namespace GeekCell\Ddd\Infrastructure\InMemory;
 
 use EmptyIterator;
-use GeekCell\Ddd\Contracts\Domain\Paginator;
+use GeekCell\Ddd\Contracts\Domain\Paginator as PaginatorInterface;
 use GeekCell\Ddd\Domain\Collection;
 use LimitIterator;
 use Traversable;
 
-class InMemoryPaginator implements Paginator
+class Paginator implements PaginatorInterface
 {
     public function __construct(
         private readonly Collection $collection,
diff --git a/src/Infrastructure/InMemory/QueryBus.php b/src/Infrastructure/InMemory/QueryBus.php
new file mode 100644
index 0000000..ab4857b
--- /dev/null
+++ b/src/Infrastructure/InMemory/QueryBus.php
@@ -0,0 +1,49 @@
+<?php
+
+declare(strict_types=1);
+
+namespace GeekCell\Ddd\Infrastructure\InMemory;
+
+use GeekCell\Ddd\Contracts\Application\Query;
+use GeekCell\Ddd\Contracts\Application\QueryBus as QueryBusInterface;
+use GeekCell\Ddd\Contracts\Application\QueryHandler;
+use GeekCell\Ddd\Support\Attributes\For\Query as ForQuery;
+
+final class QueryBus extends AbstractBus implements QueryBusInterface
+{
+    /**
+     * @inheritDoc
+     */
+    public function dispatch(Query $query): mixed
+    {
+        $queryType = get_class($query);
+        if (!array_key_exists($queryType, $this->handlers)) {
+            return null;
+        }
+
+        $handler = $this->handlers[$queryType];
+        if (is_callable($handler)) {
+            return $handler($query);
+        }
+
+        if (is_array($handler)) {
+            [$handler, $method] = $handler;
+            return call_user_func([$handler, $method], $query);
+        }
+    }
+
+    /**
+     * @inheritDoc
+     */
+    public function registerHandler(mixed $handler): void
+    {
+        if (is_callable($handler)) {
+            $this->registerCallableHandler($handler, Query::class);
+            return;
+        }
+
+        if ($handler instanceof QueryHandler) {
+            $this->registerHandlerClass($handler, ForQuery::class);
+        }
+    }
+}
diff --git a/src/Infrastructure/InMemoryRepository.php b/src/Infrastructure/InMemory/Repository.php
similarity index 89%
rename from src/Infrastructure/InMemoryRepository.php
rename to src/Infrastructure/InMemory/Repository.php
index b4759ea..7e9c866 100644
--- a/src/Infrastructure/InMemoryRepository.php
+++ b/src/Infrastructure/InMemory/Repository.php
@@ -2,14 +2,14 @@
 
 declare(strict_types=1);
 
-namespace GeekCell\Ddd\Infrastructure;
+namespace GeekCell\Ddd\Infrastructure\InMemory;
 
 use Assert\Assert;
-use GeekCell\Ddd\Contracts\Domain\Repository as Repository;
-use GeekCell\Ddd\Infrastructure\InMemoryPaginator;
+use GeekCell\Ddd\Contracts\Domain\Repository as RepositoryInterface;
+use GeekCell\Ddd\Infrastructure\InMemory\Paginator as InMemoryPaginator;
 use Traversable;
 
-abstract class InMemoryRepository implements Repository
+abstract class Repository implements RepositoryInterface
 {
     /**
      * @var T[]
diff --git a/src/Support/Attributes/For/Command.php b/src/Support/Attributes/For/Command.php
new file mode 100644
index 0000000..2d7b1b4
--- /dev/null
+++ b/src/Support/Attributes/For/Command.php
@@ -0,0 +1,18 @@
+<?php
+
+declare(strict_types=1);
+
+namespace GeekCell\Ddd\Support\Attributes\For;
+
+use Attribute;
+use GeekCell\Ddd\Contracts\Application\Command as CommandInterface;
+use GeekCell\Ddd\Support\Attributes\ForType;
+
+#[Attribute(Attribute::TARGET_CLASS)]
+class Command extends ForType
+{
+    protected function supports(): string
+    {
+        return CommandInterface::class;
+    }
+}
diff --git a/src/Support/Attributes/For/Query.php b/src/Support/Attributes/For/Query.php
new file mode 100644
index 0000000..aa8a242
--- /dev/null
+++ b/src/Support/Attributes/For/Query.php
@@ -0,0 +1,18 @@
+<?php
+
+declare(strict_types=1);
+
+namespace GeekCell\Ddd\Support\Attributes\For;
+
+use Attribute;
+use GeekCell\Ddd\Contracts\Application\Query as QueryInterface;
+use GeekCell\Ddd\Support\Attributes\ForType;
+
+#[Attribute(Attribute::TARGET_CLASS)]
+class Query extends ForType
+{
+    protected function supports(): string
+    {
+        return QueryInterface::class;
+    }
+}
diff --git a/src/Support/Attributes/ForType.php b/src/Support/Attributes/ForType.php
new file mode 100644
index 0000000..d02b48f
--- /dev/null
+++ b/src/Support/Attributes/ForType.php
@@ -0,0 +1,31 @@
+<?php
+
+declare(strict_types=1);
+
+namespace GeekCell\Ddd\Support\Attributes;
+
+abstract class ForType
+{
+    public function __construct(
+        private string $type,
+        private string $handler = 'execute',
+    ) {
+    }
+
+    public function getType(): string
+    {
+        return $this->type;
+    }
+
+    public function getHandler(): string
+    {
+        return $this->handler;
+    }
+
+    public function isValid(): bool
+    {
+        return is_subclass_of($this->getType(), $this->supports());
+    }
+
+    abstract protected function supports(): string;
+}
diff --git a/tests/Fixtures/Counter.php b/tests/Fixtures/Counter.php
new file mode 100644
index 0000000..4da66b3
--- /dev/null
+++ b/tests/Fixtures/Counter.php
@@ -0,0 +1,12 @@
+<?php
+
+declare(strict_types=1);
+
+namespace GeekCell\Ddd\Tests\Fixtures;
+
+class Counter
+{
+    public function __construct(private int $value)
+    {
+    }
+}
diff --git a/tests/Infrastructure/InMemory/CommandBusTest.php b/tests/Infrastructure/InMemory/CommandBusTest.php
new file mode 100644
index 0000000..4554d62
--- /dev/null
+++ b/tests/Infrastructure/InMemory/CommandBusTest.php
@@ -0,0 +1,114 @@
+<?php
+
+declare(strict_types=1);
+
+namespace GeekCell\Ddd\Tests\Infrastructure\InMemory;
+
+use GeekCell\Ddd\Contracts\Application\Command;
+use GeekCell\Ddd\Contracts\Application\CommandHandler;
+use GeekCell\Ddd\Infrastructure\InMemory\CommandBus as InMemoryCommandBus;
+use GeekCell\Ddd\Support\Attributes\For;
+use PHPUnit\Framework\TestCase;
+
+/**
+ * Test fixture for InMemoryCommandBus.
+ */
+class TestCommand implements Command
+{
+}
+
+/**
+ * Test fixture for InMemoryCommandBus.
+ */
+class UnknownCommand implements Command
+{
+}
+
+/**
+ * Test fixture for InMemoryCommandBus.
+ */
+#[For\Command(TestCommand::class)]
+class TestCommandHandler implements CommandHandler
+{
+    public function execute(Command $command): mixed
+    {
+        return __CLASS__;
+    }
+}
+
+/**
+ * Test fixture for InMemoryCommandBus.
+ */
+class TestCommandHandlerWithoutAttributes implements CommandHandler
+{
+    public function execute(Command $command): mixed
+    {
+        return __CLASS__;
+    }
+}
+
+/**
+ * Test fixture for InMemoryCommandBus.
+ */
+class CallableCommandHandler
+{
+    public function __invoke(TestCommand $command): mixed
+    {
+        return __CLASS__;
+    }
+}
+
+final class CommandBusTest extends TestCase
+{
+    public function testAddHandlerClass(): void
+    {
+        // Given
+        $commandBus = new InMemoryCommandBus();
+        $commandBus->registerHandler(new TestCommandHandler());
+
+        // When
+        $result = $commandBus->dispatch(new TestCommand());
+
+        // Then
+        self::assertEquals(TestCommandHandler::class, $result);
+    }
+
+    public function testAddHandlerClassWithoutAttributes(): void
+    {
+        // Given
+        $commandBus = new InMemoryCommandBus();
+        $commandBus->registerHandler(new TestCommandHandlerWithoutAttributes());
+
+        // When
+        $result = $commandBus->dispatch(new TestCommand());
+
+        // Then
+        self::assertNull($result);
+    }
+
+    public function testAddCallableHandler(): void
+    {
+        // Given
+        $commandBus = new InMemoryCommandBus();
+        $commandBus->registerHandler(new CallableCommandHandler());
+
+        // When
+        $result = $commandBus->dispatch(new TestCommand());
+
+        // Then
+        self::assertEquals(CallableCommandHandler::class, $result);
+    }
+
+    public function testAddCallableHandlerWithUnknownCommand(): void
+    {
+        // Given
+        $commandBus = new InMemoryCommandBus();
+        $commandBus->registerHandler(new CallableCommandHandler());
+
+        // When
+        $result = $commandBus->dispatch(new UnknownCommand());
+
+        // Then
+        self::assertNull($result);
+    }
+}
diff --git a/tests/Infrastructure/InMemoryPaginatorTest.php b/tests/Infrastructure/InMemory/PaginatorTest.php
similarity index 95%
rename from tests/Infrastructure/InMemoryPaginatorTest.php
rename to tests/Infrastructure/InMemory/PaginatorTest.php
index 1fc78f7..e3eaf96 100644
--- a/tests/Infrastructure/InMemoryPaginatorTest.php
+++ b/tests/Infrastructure/InMemory/PaginatorTest.php
@@ -2,23 +2,18 @@
 
 declare(strict_types=1);
 
+namespace GeekCell\Ddd\Tests\Infrastructure\InMemory;
+
+use ArrayIterator;
+use EmptyIterator;
 use GeekCell\Ddd\Domain\Collection;
-use GeekCell\Ddd\Infrastructure\InMemoryPaginator;
+use GeekCell\Ddd\Infrastructure\InMemory\Paginator as InMemoryPaginator;
+use GeekCell\Ddd\Tests\Fixtures\Counter;
+use LimitIterator;
+use Mockery;
 use PHPUnit\Framework\TestCase;
 
-/**
- * Test fixture for InMemoryPaginator.
- *
- * @package GeekCell\Ddd\Tests\Infrastructure
- */
-class Counter
-{
-    public function __construct(private int $value)
-    {
-    }
-}
-
-class InMemoryPaginatorTest extends TestCase
+class PaginatorTest extends TestCase
 {
     public function testGetCurrentPage(): void
     {
diff --git a/tests/Infrastructure/InMemory/QueryBusTest.php b/tests/Infrastructure/InMemory/QueryBusTest.php
new file mode 100644
index 0000000..425a977
--- /dev/null
+++ b/tests/Infrastructure/InMemory/QueryBusTest.php
@@ -0,0 +1,114 @@
+<?php
+
+declare(strict_types=1);
+
+namespace GeekCell\Ddd\Tests\Infrastructure\InMemory;
+
+use GeekCell\Ddd\Contracts\Application\Query;
+use GeekCell\Ddd\Contracts\Application\QueryHandler;
+use GeekCell\Ddd\Infrastructure\InMemory\QueryBus as InMemoryQueryBus;
+use GeekCell\Ddd\Support\Attributes\For;
+use PHPUnit\Framework\TestCase;
+
+/**
+ * Test fixture for InMemoryQueryBus.
+ */
+class TestQuery implements Query
+{
+}
+
+/**
+ * Test fixture for InMemoryQueryBus.
+ */
+class UnknownQuery implements Query
+{
+}
+
+/**
+ * Test fixture for InMemoryQueryBus.
+ */
+#[For\Query(TestQuery::class)]
+class TestQueryHandler implements QueryHandler
+{
+    public function execute(Query $query): mixed
+    {
+        return __CLASS__;
+    }
+}
+
+/**
+ * Test fixture for InMemoryQueryBus.
+ */
+class TestQueryHandlerWithoutAttributes implements QueryHandler
+{
+    public function execute(Query $query): mixed
+    {
+        return __CLASS__;
+    }
+}
+
+/**
+ * Test fixture for InMemoryQueryBus.
+ */
+class CallableQueryHandler
+{
+    public function __invoke(TestQuery $command): mixed
+    {
+        return __CLASS__;
+    }
+}
+
+final class QueryBusTest extends TestCase
+{
+    public function testAddHandlerClass(): void
+    {
+        // Given
+        $queryBus = new InMemoryQueryBus();
+        $queryBus->registerHandler(new TestQueryHandler());
+
+        // When
+        $result = $queryBus->dispatch(new TestQuery());
+
+        // Then
+        self::assertEquals(TestQueryHandler::class, $result);
+    }
+
+    public function testAddHandlerClassWithoutAttributes(): void
+    {
+        // Given
+        $queryBus = new InMemoryQueryBus();
+        $queryBus->registerHandler(new TestQueryHandlerWithoutAttributes());
+
+        // When
+        $result = $queryBus->dispatch(new TestQuery());
+
+        // Then
+        self::assertNull($result);
+    }
+
+    public function testAddCallableHandler(): void
+    {
+        // Given
+        $queryBus = new InMemoryQueryBus();
+        $queryBus->registerHandler(new CallableQueryHandler());
+
+        // When
+        $result = $queryBus->dispatch(new TestQuery());
+
+        // Then
+        self::assertEquals(CallableQueryHandler::class, $result);
+    }
+
+    public function testAddCallableHandlerWithUnknownCommand(): void
+    {
+        // Given
+        $queryBus = new InMemoryQueryBus();
+        $queryBus->registerHandler(new CallableQueryHandler());
+
+        // When
+        $result = $queryBus->dispatch(new UnknownQuery());
+
+        // Then
+        self::assertNull($result);
+    }
+}
diff --git a/tests/Infrastructure/InMemoryRepositoryTest.php b/tests/Infrastructure/InMemory/RepositoryTest.php
similarity index 92%
rename from tests/Infrastructure/InMemoryRepositoryTest.php
rename to tests/Infrastructure/InMemory/RepositoryTest.php
index d25b204..3d2483f 100644
--- a/tests/Infrastructure/InMemoryRepositoryTest.php
+++ b/tests/Infrastructure/InMemory/RepositoryTest.php
@@ -2,26 +2,15 @@
 
 declare(strict_types=1);
 
-namespace GeekCell\Ddd\Tests\Infrastructure;
+namespace GeekCell\Ddd\Tests\Infrastructure\InMemory;
 
 use Assert;
 use GeekCell\Ddd\Domain\Collection;
-use GeekCell\Ddd\Infrastructure\InMemoryPaginator;
-use GeekCell\Ddd\Infrastructure\InMemoryRepository;
+use GeekCell\Ddd\Infrastructure\InMemory\Paginator as InMemoryPaginator;
+use GeekCell\Ddd\Infrastructure\InMemory\Repository as InMemoryRepository;
+use GeekCell\Ddd\Tests\Fixtures\Counter;
 use PHPUnit\Framework\TestCase;
 
-/**
- * Test fixture for InMemoryRepository.
- *
- * @package GeekCell\Ddd\Tests\Infrastructure
- */
-class Counter
-{
-    public function __construct(private int $value)
-    {
-    }
-}
-
 /**
  * Test fixture for InMemoryRepository.
  *