Cachables

Cachables are data or resources that can be stored in a cache to speed up repeated access. Caching works by keeping a copy of frequently requested items close to where they are needed, allowing subsequent requests to be served from faster storage rather than reprocessing or rereading the original source. The goal of caching is to reduce latency, lower load on backend systems, and improve overall performance.

Determining cacheability depends on several factors. Cacheable items are typically deterministic and read-only or infrequently updated, so their results remain valid for a period. Personalization, rapid data changes, or highly dynamic content reduce cacheability or require segmentation by user or context. Effective cache design uses clear expiration or validation policies, such as time-to-live (TTL) values and mechanisms to revalidate cached data when it becomes stale.

Caching can occur at multiple layers. Client-side caches in web browsers store static assets and API responses. Content delivery networks (CDNs) and reverse proxies keep copies of popular resources closer to users. Application-level caches, including in-memory stores like Redis or Memcached, hold computed results or database queries for reuse. Cache keys should uniquely identify the resource and, when appropriate, the user context. Validation methods like ETag or Last-Modified, along with conditional requests, help ensure freshness.

Common cacheable resources include static assets (images, CSS, JavaScript), library files, and API responses with stable results. Best practices emphasize proper invalidation on updates, appropriate TTLs, cache-busting for assets, and safeguarding sensitive data from being cached in shared environments.