drupal-caching

Drupal Caching

Always use cache metadata on render arrays. Never return a render array without #cache keys. Check for proper cache tag, cache context, and max-age on every render array you create.

Cache Metadata (Render Arrays)

Every render array should include cache metadata:

$build = [
  '#theme' => 'my_template',
  '#data' => $data,
  '#cache' => [
    'keys' => ['my_module', 'block', $id],
    'contexts' => ['user', 'url.query_args'],
    'tags' => ['node:' . $nid, 'node_list'],
    'max-age' => 3600,
  ],
];

Cache Contexts

Context	Varies By	Use When
user	Current user ID	Content per user
user.roles	User roles	Content per role
user.permissions	Permissions	Access-dependent
url	Full URL	Page-specific
url.path	URL path only	Path-dependent
url.query_args	Query parameters	Filtered content
languages	Current language	Multilingual
theme	Active theme	Theme-specific
session	Session ID	Session-dependent

Cache Tags

// Entity-based tags (auto-invalidated).
'tags' => ['node:42']           // Specific node.
'tags' => ['node_list']         // Any node list.
'tags' => ['taxonomy_term:5']   // Specific term.
'tags' => ['config:system.site'] // Config object.

// Custom tags.
'tags' => ['my_module:feature_x']

CacheableMetadata (Object-Oriented API)

Use CacheableMetadata to merge cache metadata from multiple sources. This is cleaner than manually assembling #cache arrays, especially in complex render pipelines.

use Drupal\Core\Cache\CacheableMetadata;

// Build cache metadata from multiple sources.
$cache = new CacheableMetadata();
$cache->addCacheableDependency($node);
$cache->addCacheableDependency($user);
$cache->addCacheContexts(['url.query_args']);
$cache->addCacheTags(['my_module:feature_x']);
$cache->setCacheMaxAge(3600);

// Apply to a render array.
$cache->applyTo($build);

// Merge metadata from an access result into the render array.
$access = $entity->access('view', $account, TRUE);
$cache->addCacheableDependency($access);

Lazy Builders

Use #lazy_builder for fragments that vary per user inside otherwise cacheable pages. Lazy builders defer rendering until after the page cache is resolved, so the rest of the page can still be cached.

$build['user_greeting'] = [
  '#lazy_builder' => [
    'my_module.greeting_builder:build', // Service::method
    [$user_id],                         // Arguments (scalars only)
  ],
  '#create_placeholder' => TRUE,
];

The service must implement a build() method returning a render array:

final class GreetingBuilder {
  public function build(int $user_id): array {
    return ['#markup' => 'Hello, ' . $this->loadUserName($user_id)];
  }
}

Cache Invalidation

In services, inject CacheTagsInvalidatorInterface — never use \Drupal::service() calls.

// In a service with injected $cacheInvalidator:
$this->cacheInvalidator->invalidateTags(['node:42', 'my_module:feature_x']);

Cache Bins

Bin	Purpose
default	General-purpose
render	Render arrays
page	Full page cache
dynamic_page_cache	Authenticated pages
discovery	Plugin discovery
data	Data processing
config	Configuration
menu	Menu trees

External Cache Backends

Redis Configuration

// settings.php
$settings['redis.connection']['interface'] = 'PhpRedis';
$settings['redis.connection']['host'] = '127.0.0.1';
$settings['cache']['default'] = 'cache.backend.redis';

Varnish Headers

// Ensure proper cache headers.
$response->headers->set('Cache-Control', 'public, max-age=3600');
$response->headers->set('Surrogate-Control', 'max-age=86400');

Caching Layers

1. Internal Page Cache - Anonymous users (built-in).
2. Dynamic Page Cache - Authenticated users (built-in).
3. Render Cache - Render arrays (#cache).
4. Cache Backends - Redis, Memcached.
5. Reverse Proxy - Varnish, CDN.

Avoiding N+1 Queries

// Bad: N queries.
foreach ($nids as $nid) {
  $node = Node::load($nid);
}

// Good: 1 query.
$nodes = Node::loadMultiple($nids);

Performance Checklist

• CSS/JS aggregation enabled in production.
• Redis/Memcache configured for cache backend.
• No N+1 query problems.
• Image optimization enabled (WebP, lazy loading).
• BigPipe enabled for authenticated users.
• Entity queries use accessCheck() explicitly.
• Views use caching with appropriate tags.