Node.js Redis Caching

What is Redis Caching in Node.js?

Redis is an in-memory data store used for caching, sessions, rate-limit counters and queues. Caching an expensive query in Redis turns a slow endpoint into a fast one without changing the database.

Redis Caching example

import { createClient } from 'redis';
const redis = createClient({ url: process.env.REDIS_URL });
await redis.connect();

async function getJobsByCity(city) {
  const key = `jobs:city:${city}`;

  const cached = await redis.get(key);
  if (cached) return JSON.parse(cached);

  const jobs = await Job.find({ city, status: 'active' }).lean();
  await redis.setEx(key, 300, JSON.stringify(jobs));   // expire in 5 minutes
  return jobs;
}

// invalidate when the data changes
await redis.del(`jobs:city:${job.city}`);

Key points to remember

• Always set an expiry — an unbounded cache eventually exhausts memory.
• Choose a key naming convention such as entity:field:value from day one.
• Invalidate on write, or accept staleness for the length of the TTL.
• Redis is also where sessions and rate-limit counters belong in a clustered app.

Common mistakes with Redis Caching

• Caching without expiry and serving stale data indefinitely.
• Caching per-user data under a shared key, leaking one user’s data to another.