What is caching?
Caching is a technique where copies of frequently accessed data are stored in a fast, temporary location so that future requests for that data can be served quickly without having to fetch the original source each time.
Let's break it down
- Cache storage: a small, fast memory area (RAM, SSD, or even a browser’s local storage).
- Cache key: a unique identifier that tells the system which piece of data is being stored.
- Cache hit: when the requested data is found in the cache, so it can be returned instantly.
- Cache miss: when the data isn’t in the cache, so the system must retrieve it from the original source and then usually store a copy for next time.
- Eviction policy: rules (like Least Recently Used) that decide which items to remove when the cache gets full.
Why does it matter?
Caching makes applications run faster, reduces the load on servers or databases, saves bandwidth, and improves the overall user experience by delivering content almost instantly.
Where is it used?
- Web browsers cache images, scripts, and pages.
- Content Delivery Networks (CDNs) cache static files close to users.
- Databases use query caches to store results of frequent queries.
- Operating systems cache disk reads in RAM.
- Applications often cache API responses or computed results.
Good things about it
- Speed: Data is served in milliseconds instead of seconds.
- Efficiency: Less work for servers and databases, lowering costs.
- Scalability: Helps handle more users without adding extra hardware.
- Reliability: Can provide data even when the original source is temporarily unavailable.
Not-so-good things
- Stale data: Cached information can become outdated if not refreshed properly.
- Complexity: Implementing and managing cache invalidation adds development overhead.
- Memory usage: Caches consume RAM or storage that could be needed elsewhere.
- Cache misses: Poorly designed caches can still result in many misses, reducing benefits.