1. What It Is
Application caching stores computed results, database query results, or API responses in fast storage so future requests can be served without repeating expensive work.
The problem it solves: Databases, external APIs, and complex computations are slow. If your API fetches the same user profile from the database on every request, you're paying the same cost repeatedly. Caching stores the result once and serves subsequent requests in microseconds instead of milliseconds.
Why you should care: Caching is one of the most impactful performance optimizations in backend engineering. Done well, it dramatically reduces database load, improves response times, and enables your system to scale further. Done poorly, it causes stale data bugs, cache poisoning, and hard-to-debug inconsistencies.
Distinction from HTTP caching: HTTP caching (covered in the HTTP Headers topic) is controlled via HTTP headers and lives in browsers and CDNs. Application caching is server-side logic — Redis, Memcached, in-process memory — under your full control.
In the full tutorial
- 2. How It Works in Practice
- 3. Common Real-World Usage
- 4. Trade-offs and Common Mistakes
- 5. Interview Angle
- 6. Practical Examples