Project 2 — Node.js Catalog Cache

What you'll walk away with

Explain the core ideas behind Project 2 — Node.js Catalog Cache
Run the sample Redis command or code and verify its output
Apply the technique correctly to the Tutorial Platform and production scenarios

Build the mental model

A production cache wrapper centralizes serialization, timeouts, key versions, TTL jitter, metrics, and error policy. Callers receive typed values or null without knowing Redis details. Separate cache errors from database errors and observe hits, misses, errors, and load latency.

Connect it to a real scenario

Using a Node.js Redis client, write a generic `getOrLoad<T>` helper. Delete malformed cached values, protect loaders with a bounded single-flight lock, and invalidate after database update commits. Integration-test hit, miss, expiry, update, and Redis-down cases.

Centralize a typed cache wrapper
Include timeouts, metrics, and fallback
Integration-test cache correctness

Try the working example

typescript

async function getOrLoad<T>(key: string, load: () => Promise<T | null>) {
  try {
    const hit = await redis.get(key);
    if (hit) return JSON.parse(hit) as T;
  } catch (error) { metrics.cacheError.inc(); }
  const value = await load();
  if (value) await redis.set(key, JSON.stringify(value), { EX: 300 + randomInt(30) });
  return value;
}

You should see

You get a typed catalog service that remains correct when cache is unavailable.

5-minute try-it

Add 15-second negative caching for missing tutorials and test create-after-miss behavior.

One important caution

If the Redis timeout consumes the HTTP deadline, no time remains for fallback; keep cache timeouts short.

Redis — Node.js Client Guide — Redis

Easy traps

If the Redis timeout consumes the HTTP deadline, no time remains for fallback; keep cache timeouts short.
Validate sample commands on a local or test instance with recoverable data before applying them to production Redis.

Exercise

Add 15-second negative caching for missing tutorials and test create-after-miss behavior.

You'll know it worked when: You get a typed catalog service that remains correct when cache is unavailable.