diff --git a/module/Rest/config/initial-api-key.config.php b/module/Rest/config/initial-api-key.config.php
index 57114479..a44f877f 100644
--- a/module/Rest/config/initial-api-key.config.php
+++ b/module/Rest/config/initial-api-key.config.php
@@ -11,6 +11,8 @@ use const PHP_SAPI;
 
 return [
 
+    // We will try to load the initial API key only for openswoole and RoadRunner.
+    // For php-fpm, the check against the database would happen on every request, resulting in a very bad performance.
     'initial_api_key' => PHP_SAPI !== 'cli' ? null : EnvVars::INITIAL_API_KEY->loadFromEnv(),
 
     'dependencies' => [
diff --git a/module/Rest/test/ApiKey/InitialApiKeyDelegatorTest.php b/module/Rest/test/ApiKey/InitialApiKeyDelegatorTest.php
new file mode 100644
index 00000000..7614fc9d
--- /dev/null
+++ b/module/Rest/test/ApiKey/InitialApiKeyDelegatorTest.php
@@ -0,0 +1,61 @@
+<?php
+
+declare(strict_types=1);
+
+namespace ShlinkioTest\Shlink\Rest\ApiKey;
+
+use Doctrine\ORM\EntityManager;
+use Doctrine\ORM\EntityManagerInterface;
+use Mezzio\Application;
+use PHPUnit\Framework\TestCase;
+use Prophecy\Argument;
+use Prophecy\PhpUnit\ProphecyTrait;
+use Prophecy\Prophecy\ObjectProphecy;
+use Psr\Container\ContainerInterface;
+use Shlinkio\Shlink\Rest\ApiKey\InitialApiKeyDelegator;
+use Shlinkio\Shlink\Rest\ApiKey\Repository\ApiKeyRepositoryInterface;
+use Shlinkio\Shlink\Rest\Entity\ApiKey;
+
+class InitialApiKeyDelegatorTest extends TestCase
+{
+    use ProphecyTrait;
+
+    private InitialApiKeyDelegator $delegator;
+    private ObjectProphecy $container;
+
+    protected function setUp(): void
+    {
+        $this->delegator = new InitialApiKeyDelegator();
+        $this->container = $this->prophesize(ContainerInterface::class);
+    }
+
+    /**
+     * @test
+     * @dataProvider provideConfigs
+     */
+    public function apiKeyIsInitializedWhenAppropriate(array $config, int $expectedCalls): void
+    {
+        $app = $this->prophesize(Application::class)->reveal();
+        $apiKeyRepo = $this->prophesize(ApiKeyRepositoryInterface::class);
+        $em = $this->prophesize(EntityManagerInterface::class);
+
+        $getConfig = $this->container->get('config')->willReturn($config);
+        $getRepo = $em->getRepository(ApiKey::class)->willReturn($apiKeyRepo->reveal());
+        $getEm = $this->container->get(EntityManager::class)->willReturn($em->reveal());
+
+        $result = ($this->delegator)($this->container->reveal(), '', fn () => $app);
+
+        self::assertSame($result, $app);
+        $getConfig->shouldHaveBeenCalledOnce();
+        $getRepo->shouldHaveBeenCalledTimes($expectedCalls);
+        $getEm->shouldHaveBeenCalledTimes($expectedCalls);
+        $apiKeyRepo->createInitialApiKey(Argument::any())->shouldHaveBeenCalledTimes($expectedCalls);
+    }
+
+    public function provideConfigs(): iterable
+    {
+        yield [[], 0];
+        yield [['initial_api_key' => null], 0];
+        yield [['initial_api_key' => 'the_initial_key'], 1];
+    }
+}