Have you had experience implementing and using caching in Node.js applications?

Yes, I have experience implementing caching in Node.js applications to improve performance and reduce load on databases or external APIs.

Most often, I used Redis as an external cache, as well as built-in in-memory cache for small tasks. For example, when querying a database, you can first check the cache, and if the data is there — return it, otherwise fetch from the database and store in the cache.

An example using Redis and the redis library:

const redis = require('redis');
const client = redis.createClient();

async function getUser(userId) {
  const cacheKey = `user:${userId}`;
  const cached = await client.get(cacheKey);
  if (cached) {
    return JSON.parse(cached);
  }
  const user = await db.getUserById(userId); // database query
  await client.set(cacheKey, JSON.stringify(user), 'EX', 3600); // cache for 1 hour
  return user;
}

This approach significantly reduces response time and load on the database.