Cache Aside

The Cache Aside pattern is a caching technique where the application first checks if the requested data exists in the cache. If it does, the cache returns the data immediately. If the data is not in the cache (a “cache miss”), the application retrieves it from the database, stores a copy in the cache for future use, and then returns the data to the user. This pattern gives the application full control over when data is cached and evicted.

This approach is beneficial when data is read frequently but written to infrequently, as it minimizes database load. It’s also useful when the data source is slow or expensive to access. The application is responsible for maintaining cache consistency, typically through cache invalidation strategies when the underlying data changes.

Usage

The Cache Aside pattern is widely used in scenarios where:

• Read-heavy applications: Websites, APIs, and applications that primarily read data benefit from reduced database load.
• Slow data sources: When fetching data from a database, external API, or other slow source, caching can significantly improve response times.
• Distributed systems: Caching can reduce network traffic and improve performance in distributed environments.
• Session Management: Storing user session data in a cache (like Redis) for fast access.

Examples

• Redis: Redis is a popular in-memory data store often used as a cache with the Cache Aside pattern. Applications explicitly check Redis for data and populate it if a miss occurs. Many web frameworks have built-in integration with Redis for easy implementation.
• Memcached: Similar to Redis, Memcached is a distributed memory object caching system. Applications use client libraries to interact with Memcached, following the Cache Aside pattern to retrieve and store data.
• Content Delivery Networks (CDNs): CDNs cache static assets (images, CSS, JavaScript) closer to users. When a user requests an asset, the CDN checks its cache. If it’s a miss, the CDN fetches the asset from the origin server, caches it, and then delivers it to the user. This is a large-scale implementation of Cache Aside.
• Hibernate (Second Level Cache): While Hibernate also supports other caching strategies, it can be used with Cache Aside through integration with external caching providers, allowing applications to manage data retrieval and caching.