Drupal Caching

Philosophy: Configuration first. Prioritize declarative caching (cache metadata in render arrays, config schema for cache backends) over programmatic approaches.

I need to...

I need to...	Guide	Summary
Understand Drupal's caching layers and when to use each	Cache System Overview	When you need to understand which caching layer to use for different scenarios — page cache for anonymous users, dynamic page cache for authenticated users, render cache for reusable components, or programmatic cache bins for custom data.
Learn the three pillars of cache metadata	Cache Metadata Trinity	Every time you cache a render array or create a cacheable dependency. All three metadata properties — cache tags, cache contexts, and max-age — must be considered together.
Add cache tags to invalidate on entity/config changes	Cache Tags	When you need to invalidate cached content when specific data changes. Cache tags declare "this cached item depends on X" — when X changes, Drupal automatically invalidates all cache entries with that tag.
Vary cached content by URL, user, language, etc.	Cache Contexts	When cached content varies based on request context. Cache contexts create separate cache entries for different variations — e.g., one cached version per language, per user role, per URL path.
Set how long content can be cached	Cache Max-Age	When you need to set expiration on cached content. Max-age is the third pillar of cache metadata (alongside tags and contexts) and controls how long cached data remains valid.
Choose and configure a cache backend (Redis, Memcache, APCu)	Cache Backends	When you need to choose where cached data is stored. Cache backends determine storage mechanism — database (default), memory (APCu, Redis, Memcache), or specialized backends (chained, null).
Understand cache bins and their purposes	Cache Bins	When you need to understand where different types of cached data are stored. Cache bins are logical containers for cache data — each bin can use a different backend, have different expiration policies, and serve different purposes.
Cache render arrays and understand render caching	Render Caching	When you need to cache rendered output of render arrays. Render caching stores the final rendered HTML along with cache metadata, avoiding expensive re-rendering on subsequent requests.
Handle cache metadata bubbling in nested render arrays	BubbleableMetadata & Cache Bubbling	When you need to propagate cache metadata from child render arrays to parent. Cache bubbling ensures that when a parent element is cached, it includes all cacheability requirements from its children.
Defer expensive rendering with placeholders	Lazy Builders	When you need to defer expensive or user-specific rendering until after the main page is cached. Lazy builders create placeholders in cached content that are replaced with personalized or dynamic content during rendering.
Understand anonymous page caching	Page Cache	When you need to cache full HTML pages for anonymous users. Page Cache (Internal Page Cache module) stores complete rendered pages, serving them without bootstrapping Drupal.
Cache pages for authenticated users	Dynamic Page Cache	When you need to cache pages for authenticated users or pages with personalized content. Dynamic Page Cache caches page structure while excluding personalized parts (converted to placeholders).
Progressively render expensive content	BigPipe	When you need to progressively render expensive content. BigPipe sends page skeleton immediately, then streams placeholder replacements as they become ready, improving perceived performance.
Invalidate caches when data changes	Cache Invalidation Patterns	When you need to clear cached data when source data changes. Cache invalidation removes stale cache entries using cache tags, programmatic deletion, or time-based expiration.
Create and invalidate custom cache tags	Custom Cache Tags	When you need to invalidate cached content based on non-entity data. Custom cache tags let you create invalidation triggers for API data, computed values, or external resources.
Configure Redis or Memcache backends in settings.php	Cache Backend Configuration	When you need to configure cache backends (Redis, Memcache, APCu) in settings.php. Backend configuration determines where cached data is stored and how it's accessed.
Follow caching best practices	Best Practices & Patterns	When you need proven patterns for effective caching. These practices maximize cache hit rates, minimize stale content, and maintain performance.
Avoid common caching mistakes	Anti-Patterns & Common Mistakes	When you need to avoid common caching mistakes that cause bugs, performance issues, or stale content.
Ensure cache security and performance	Security & Performance	When you need to ensure cache security and optimal performance. Caching affects both security (sensitive data leakage) and performance (cache hit rates, memory usage).
Find core cache files and APIs	Code Reference Map