<strong>Caching</strong> is storing frequently accessed data in a fast-access location to avoid repeatedly fetching it from the original source. It dramatically improves performance and reduces server load.
The Grocery Shopping Analogy
You don't go to the grocery store every time you need milk. You store it in your fridge (cache) for quick access. Only when it runs out do you go back to the store (database).
Grocery Store (Database)
Original source
Fridge (Cache)
Quick access storage
Kitchen (App)
Where you use it
Needs Data
Check Cache First
Fallback Source
Request comes in
App needs user profile data
Check cache first
Look in Redis/memory cache
Cache hit or miss
Found in cache? Return it. Not found? Continue
Fetch from database
Query the original data source
Store in cache
Save result in cache for next time
Wrong
"Caching is just for big websites" or "Cache everything forever"
Correct
Caching benefits <strong>any application</strong>, but requires strategy: set appropriate expiration times, invalidate stale data, and cache the right things. Not all data should be cached.
Netflix using caching:
Popular shows are cached on CDN servers near you
Instead of fetching from main servers, you get it from nearby cache
Reduces latency from 500ms to 20ms
Saves bandwidth and improves user experience dramatically