Redis Caching Patterns That Actually Help

Cache-aside in 20 lines

async function getProduct(id) {
  const hit = await redis.get(`product:${id}`);
  if (hit) return JSON.parse(hit);
  const doc = await Product.findById(id).lean();
  if (doc) await redis.set(`product:${id}`, JSON.stringify(doc), "EX", 300);
  return doc;
}

TTL discipline

• Hot, slow-changing data: 5 to 15 minutes.
• Sessions and OTPs: short TTLs, let Redis do the expiry.
• Never cache without a TTL. Never.

Stampede protection

When a hot key expires, fifty requests can dogpile Mongo at once. The cheap fix: stale-while-revalidate, serve the stale copy and refresh in the background.

Cache the reads that hurt. Measure first, cache second.