diff --git a/Classes/Domain/Repository/ApiResourceRepository.php b/Classes/Domain/Repository/ApiResourceRepository.php
index 40ec8ec2..0ff4e34f 100644
--- a/Classes/Domain/Repository/ApiResourceRepository.php
+++ b/Classes/Domain/Repository/ApiResourceRepository.php
@@ -17,6 +17,14 @@ class ApiResourceRepository
 {
     protected ?FrontendInterface $cache;
 
+    /**
+     * API resources already read in this process, by cache identifier. `getByEntity()` runs for every serialized
+     * entity, so reading and unserializing the cache entry on each call would make large collections slow.
+     *
+     * @var array<string, ApiResource[]>
+     */
+    protected array $apiResourcesByCacheIdentifier = [];
+
     public function __construct(
         protected readonly CacheManager $cacheManager,
         protected readonly ReflectionService $reflectionService,
@@ -32,6 +40,14 @@ public function getAll(): array
     {
         $cacheIdentifier = $this->buildCacheIdentifier();
 
+        return $this->apiResourcesByCacheIdentifier[$cacheIdentifier] ??= $this->loadAll($cacheIdentifier);
+    }
+
+    /**
+     * @return ApiResource[]
+     */
+    protected function loadAll(string $cacheIdentifier): array
+    {
         $apiResources = $this->cache->get($cacheIdentifier);
 
         if ($apiResources !== false) {
diff --git a/Tests/Functional/Dispatcher/ApiResourceCacheDispatcherTest.php b/Tests/Functional/Dispatcher/ApiResourceCacheDispatcherTest.php
new file mode 100644
index 00000000..df147e19
--- /dev/null
+++ b/Tests/Functional/Dispatcher/ApiResourceCacheDispatcherTest.php
@@ -0,0 +1,51 @@
+<?php
+
+declare(strict_types=1);
+
+namespace SourceBroker\T3api\Tests\Functional\Dispatcher;
+
+use PHPUnit\Framework\Attributes\Test;
+use SourceBroker\T3api\Tests\Functional\Fixtures\ReadCountingCacheBackend;
+use TYPO3\CMS\Core\Cache\CacheManager;
+use TYPO3\CMS\Core\Cache\Frontend\VariableFrontend;
+
+class ApiResourceCacheDispatcherTest extends AbstractDispatcherTestCase
+{
+    protected array $configurationToUseInTestInstance = [
+        'SYS' => [
+            'caching' => [
+                'cacheConfigurations' => [
+                    't3api' => [
+                        'frontend' => VariableFrontend::class,
+                        'backend' => ReadCountingCacheBackend::class,
+                        'groups' => ['system'],
+                    ],
+                ],
+            ],
+        ],
+    ];
+
+    protected function setUp(): void
+    {
+        parent::setUp();
+        $this->importCSVDataSet(__DIR__ . '/../Fixtures/products.csv');
+        $this->importCSVDataSet(__DIR__ . '/../Fixtures/categories.csv');
+        $this->importCSVDataSet(__DIR__ . '/../Fixtures/tags.csv');
+    }
+
+    #[Test]
+    public function collectionWithRelatedResourcesReadsApiResourcesFromCacheOnce(): void
+    {
+        $this->dispatchGet('https://example.com/_api/products');
+
+        self::assertSame(1, $this->getT3apiCacheBackend()->readCount);
+    }
+
+    private function getT3apiCacheBackend(): ReadCountingCacheBackend
+    {
+        $backend = $this->get(CacheManager::class)->getCache('t3api')->getBackend();
+        self::assertInstanceOf(ReadCountingCacheBackend::class, $backend);
+
+        return $backend;
+    }
+}
diff --git a/Tests/Functional/Fixtures/ReadCountingCacheBackend.php b/Tests/Functional/Fixtures/ReadCountingCacheBackend.php
new file mode 100644
index 00000000..810d0f1e
--- /dev/null
+++ b/Tests/Functional/Fixtures/ReadCountingCacheBackend.php
@@ -0,0 +1,25 @@
+<?php
+
+declare(strict_types=1);
+
+namespace SourceBroker\T3api\Tests\Functional\Fixtures;
+
+use TYPO3\CMS\Core\Cache\Backend\TransientMemoryBackend;
+
+/**
+ * Counts reads of cache entries, e.g. to check how often one request reads the API resources.
+ */
+final class ReadCountingCacheBackend extends TransientMemoryBackend
+{
+    public int $readCount = 0;
+
+    /**
+     * @param string $entryIdentifier
+     */
+    public function get($entryIdentifier): mixed
+    {
+        $this->readCount++;
+
+        return parent::get($entryIdentifier);
+    }
+}
diff --git a/Tests/Unit/Domain/Repository/ApiResourceRepositoryTest.php b/Tests/Unit/Domain/Repository/ApiResourceRepositoryTest.php
new file mode 100644
index 00000000..11a1bb76
--- /dev/null
+++ b/Tests/Unit/Domain/Repository/ApiResourceRepositoryTest.php
@@ -0,0 +1,105 @@
+<?php
+
+declare(strict_types=1);
+
+namespace SourceBroker\T3api\Tests\Unit\Domain\Repository;
+
+use PHPUnit\Framework\Attributes\Test;
+use SourceBroker\T3api\Domain\Repository\ApiResourceRepository;
+use SourceBroker\T3api\Factory\ApiResourceFactory;
+use SourceBroker\T3api\Routing\Enhancer\ResourceEnhancer;
+use SourceBroker\T3api\Service\ReflectionService;
+use SourceBroker\T3api\Service\SiteService;
+use TYPO3\CMS\Core\Cache\CacheManager;
+use TYPO3\CMS\Core\Cache\Frontend\FrontendInterface;
+use TYPO3\CMS\Core\Http\ServerRequest;
+use TYPO3\CMS\Core\Site\Entity\Site;
+use TYPO3\TestingFramework\Core\Unit\UnitTestCase;
+
+class ApiResourceRepositoryTest extends UnitTestCase
+{
+    /**
+     * @var string[]
+     */
+    private array $readCacheIdentifiers = [];
+
+    private Site $site;
+
+    protected function setUp(): void
+    {
+        parent::setUp();
+        SiteService::reset();
+        $this->site = new Site('test', 1, [
+            'base' => 'https://example.com/',
+            'languages' => [
+                ['languageId' => 0, 'title' => 'English', 'base' => '/', 'locale' => 'en_US.UTF-8'],
+                ['languageId' => 1, 'title' => 'German', 'base' => '/de/', 'locale' => 'de_DE.UTF-8'],
+            ],
+            'routeEnhancers' => [
+                'T3api' => ['type' => ResourceEnhancer::ENHANCER_NAME, 'basePath' => '_api'],
+            ],
+        ]);
+    }
+
+    protected function tearDown(): void
+    {
+        unset($GLOBALS['TYPO3_REQUEST']);
+        SiteService::reset();
+        parent::tearDown();
+    }
+
+    #[Test]
+    public function getByEntityReadsCacheOnlyOnceForManyEntities(): void
+    {
+        $this->setCurrentRequestLanguage(0);
+        $apiResourceRepository = $this->createApiResourceRepository();
+
+        $apiResourceRepository->getByEntity(\stdClass::class);
+        $apiResourceRepository->getByEntity(\stdClass::class);
+        $apiResourceRepository->getByEntity(\stdClass::class);
+
+        self::assertSame(['ApiResourceRepository_getAll_api'], $this->readCacheIdentifiers);
+    }
+
+    #[Test]
+    public function getAllReadsCacheOncePerApiBasePath(): void
+    {
+        $apiResourceRepository = $this->createApiResourceRepository();
+
+        foreach ([0, 1, 0, 1] as $languageId) {
+            $this->setCurrentRequestLanguage($languageId);
+            $apiResourceRepository->getAll();
+        }
+
+        self::assertSame(
+            ['ApiResourceRepository_getAll_api', 'ApiResourceRepository_getAllde_api'],
+            $this->readCacheIdentifiers
+        );
+    }
+
+    private function createApiResourceRepository(): ApiResourceRepository
+    {
+        $cache = self::createStub(FrontendInterface::class);
+        $cache->method('get')->willReturnCallback(function (string $cacheIdentifier): array {
+            $this->readCacheIdentifiers[] = $cacheIdentifier;
+
+            return [];
+        });
+        $cacheManager = self::createStub(CacheManager::class);
+        $cacheManager->method('getCache')->willReturnMap([['t3api', $cache]]);
+
+        return new ApiResourceRepository(
+            $cacheManager,
+            self::createStub(ReflectionService::class),
+            self::createStub(ApiResourceFactory::class)
+        );
+    }
+
+    private function setCurrentRequestLanguage(int $languageId): void
+    {
+        $language = $this->site->getLanguageById($languageId);
+        $GLOBALS['TYPO3_REQUEST'] = (new ServerRequest($language->getBase() . '_api/news/news', 'GET'))
+            ->withAttribute('site', $this->site)
+            ->withAttribute('language', $language);
+    }
+}