Redis is an in-memory data store — a tool that keeps data in memory instead of on disk, so reading it is extremely fast. Developers use it most often as a cache: a place to keep frequently needed results so the app does not have to ask the main database every single time.

How does it work? Your app first checks Redis for an answer. If the answer is there, it is returned in milliseconds. If it is not there, the app asks the database, saves the result in Redis for next time, and returns it. The next visitor with the same request gets the fast, cached answer. Each cached item can have an expiry time, so old data disappears on its own instead of going stale forever.

A simple workflow looks like this. First, run Redis locally or use a small hosted instance. Second, pick one slow, repeated query in your app — for example, a list of popular posts or a user profile that is loaded on every page. Third, store that result in Redis with a short expiry, such as five minutes.…