A proxy cache stores an eligible response and reuses it for later requests. Done well, this reduces origin work and network latency. Done badly, it can serve stale information or one user's private response to another.
Freshness and revalidation
Cache-Control directives describe whether a response may be stored and for how long. Validators such as ETag allow a cache to ask whether its copy is still current.
The cache key matters
A shared cache must vary on every request property that changes the representation. Missing language, encoding or authorization differences can produce incorrect content.
Protect private responses
Do not cache personalized dashboards, password resets or authenticated data in a public cache unless the design explicitly isolates users. Test logout and account switching.
Measure before expanding
Track hit ratio, age, origin load and purge behavior. Cache stable public assets first; add dynamic content only with documented invalidation.
Purge is part of publishing
Teams need a tested way to invalidate an incorrect or sensitive response quickly. Versioned asset filenames reduce purge needs, while editorial pages may require targeted URL invalidation.
Observe the decision
Expose safe cache-status headers and inspect Age, Vary and Cache-Control during tests. A fast response is not necessarily a correct cache hit, and a miss is not automatically a performance failure.
Cache only responses whose rules you understand
Public static assets are good candidates. Personalized pages, authenticated responses, shopping carts and private API data require careful Cache-Control, Vary and cookie handling. A cache key that ignores authorization or language can serve one user's result to another.
Validate correctness before celebrating speed
Inspect Age, Cache-Control, Vary and a safe cache-status header across a hit, miss, revalidation and purge. Change the resource and confirm that users receive the intended version. Versioned filenames simplify static deployments; editorial fixes may require targeted invalidation.
Cache performance is a measured trade-off among freshness, origin load and latency. “Cache everything” is not a production strategy.
Sources and further reading
Use the right privacy tool for the task
A browser proxy changes the network path for one session. Review the Privacy Policy and use a trusted direct connection for sensitive accounts.