Caching Strategies

Caching Strategies for Rails 8

Overview

Rails provides multiple caching layers:

• Fragment caching: Cache view partials
• Russian doll caching: Nested cache fragments
• Low-level caching: Cache arbitrary data
• HTTP caching: Browser and CDN caching
• Query caching: Automatic within requests

Quick Start

# config/environments/development.rb
config.action_controller.perform_caching = true
config.cache_store = :memory_store

# config/environments/production.rb
config.cache_store = :solid_cache_store  # Rails 8 default
# OR
config.cache_store = :redis_cache_store, { url: ENV["REDIS_URL"] }

Enable caching in development:

bin/rails dev:cache

Cache Store Options

| Store | Use Case | Pros | Cons | |-------|----------|------|------| | :memory_store | Development | Fast, no setup | Not shared, limited size | | :solid_cache_store | Production (Rails 8) | Database-backed, no Redis | Slightly slower | | :redis_cache_store | Production | Fast, shared | Requires Redis | | :file_store | Simple production | Persistent, no Redis | Slow, not shared | | :null_store | Testing | No caching | N/A |

Fragment Caching

Basic Fragment Cache

Cache Key Components

Rails generates cache keys from:

• Model name
• Model ID
• updated_at timestamp
• Template digest (automatic)

# Generated key example:
# views/events/123-20240115120000000000/abc123digest

Custom Cache Keys

  ...

  ...

  

Russian Doll Caching

Nested caches where inner caches are reused when outer cache is invalidated:

Use touch: true on belongs_to associations to cascade invalidation up the chain. See [cache-invalidation.md](references/cache-invalidation.md) for examples.

Collection Caching

Efficient Collection Rendering

(event) { [event, current_user.admin?] } %>

Low-Level Caching

Use Rails.cache.fetch with a block for the most common pattern. See [low-level-caching.md](references/low-level-caching.md) for:

• Basic read/write/fetch examples
• Caching in service objects
• Caching in query objects
• Instance variable memoization
• Request-scoped memoization with CurrentAttributes

Cache Invalidation

Three strategies: time-based expiration, key-based expiration (using updated_at), and manual deletion. See [cache-invalidation.md](references/cache-invalidation.md) for:

• Time-based and key-based expiration
• Manual invalidation in model callbacks and services
• Pattern-based deletion (delete_matched)
• touch: true for Russian doll cascade
• Built-in and custom counter caches

HTTP Caching

Use stale? for conditional GET (ETags/Last-Modified) and expires_in for Cache-Control headers. See [http-caching-and-testing.md](references/http-caching-and-testing.md) for full examples.

Testing Caching

Use a :caching metadata tag to enable caching in specs. See [http-caching-and-testing.md](references/http-caching-and-testing.md) for:

• rails_helper.rb configuration
• Testing cached view invalidation
• Testing cache invalidation in services
• Performance monitoring and instrumentation

Checklist

• [ ] Cache store configured for environment
• [ ] Fragment caching on expensive partials
• [ ] touch: true on belongs_to for Russian doll
• [ ] Collection caching with cached: true
• [ ] Low-level caching for expensive queries
• [ ] Cache invalidation strategy defined
• [ ] Counter caches for counts
• [ ] HTTP caching headers for API
• [ ] Cache warming for cold starts (if needed)
• [ ] Monitoring for hit/miss rates

References

• [low-level-caching.md](references/low-level-caching.md) - fetch/read/write, service objects, query objects, memoization
• [cache-invalidation.md](references/cache-invalidation.md) - expiration strategies, manual invalidation, touch, counter caches
• [http-caching-and-testing.md](references/http-caching-and-testing.md) - ETags, Cache-Control, spec configuration, monitoring

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: ThibautBaissac
• Source: ThibautBaissac/railsai_agents
• License: MIT
• Homepage: https://thibautbaissac.github.io/

Install and usage instructions live in the source repository linked above.