Redis as Cache: 30-Minute Tutorial

Redis is the simplest cache. The walkthrough gets you to measurable latency improvement.

Step 1: Run Redis

docker run -d -p 6379:6379 redis

Verify: redis-cli ping → PONG.

Step 2: Cache-aside in Python

• def get_user(uid):
      cached = r.get(f"user:{uid}")
      if cached: return json.loads(cached)
      user = db.fetch(uid)
      r.setex(f"user:{uid}", 60, json.dumps(user))
      return user

Step 3: Measure

First call: 50ms (DB hit).

Second call: 0.5ms (cache hit).

100x speedup on cached path.

Step 4: TTL and invalidation

setex sets TTL.

On update: r.delete(f"user:{uid}") to invalidate.

Pattern: write-through invalidation.

Antipatterns

• No TTL. Stale forever.
• Cache without invalidation. Data drift.
• Caching everything. Memory exhaustion.

What to do this week

Three moves. (1) Run the tutorial end-to-end on your own laptop / sandbox. (2) Apply the pattern to one production workload. (3) Document the variations you needed; share with the team.