What is Caching?
Storing frequently accessed data closer to where it's needed so it doesn't have to be computed or fetched from the database every time.
In plain English
Like keeping your most-used ingredients on the kitchen counter instead of walking to the pantry every time. The food is the same, but getting it is much faster. Caching trades a small amount of storage for a large improvement in speed.
Types of caching
Browser caching: static assets (images, CSS, JS) stored in the user's browser. CDN caching: content served from servers geographically close to the user. Server-side caching: frequently queried data stored in memory (Redis, in-memory cache). Application caching: computed results stored to avoid re-computation. Database caching: query results cached to avoid repeated database hits.
When to cache
Data that's read frequently but changes rarely (product listings, user profiles, configuration). Expensive computations (analytics aggregations, search results). Static assets that don't change between deployments. API responses from external services with rate limits.
Cache invalidation
The hardest part of caching is knowing when to update it. If a user changes their profile, the cached version needs to update too. Strategies: set a Time-To-Live (TTL) so caches expire automatically, invalidate specific cache keys when data changes, or use stale-while-revalidate to serve cached data while fetching fresh data in the background.
Frequently asked questions
How do I add caching to my Next.js app?
Next.js has built-in caching: static pages are cached automatically, fetch() requests can be cached with options, and you can use unstable_cache for data caching. For more control, add Redis via Upstash (serverless-friendly) for custom caching. For static assets, your hosting platform (Vercel, Netlify) handles CDN caching automatically.
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