Redis Patterns

Caching Strategies

async function getUser(userId: string): Promise<User> {
  const cacheKey = `user:${userId}`;
  const cached = await redis.get(cacheKey);

  if (cached) {
    return JSON.parse(cached);
  }

  const user = await db.user.findUnique({ where: { id: userId } });
  if (user) {
    await redis.set(cacheKey, JSON.stringify(user), "EX", 3600);
  }

  return user;
}

async function invalidateUser(userId: string): Promise<void> {
  await redis.del(`user:${userId}`);
  await redis.del(`user:${userId}:orders`);
}

async function cacheAside<T>(
  key: string,
  ttlSeconds: number,
  fetcher: () => Promise<T>
): Promise<T> {
  const cached = await redis.get(key);
  if (cached) return JSON.parse(cached);

  const value = await fetcher();
  await redis.set(key, JSON.stringify(value), "EX", ttlSeconds);
  return value;
}

Rate Limiting with Sliding Window

async function isRateLimited(
  clientId: string,
  limit: number,
  windowSeconds: number
): Promise<boolean> {
  const key = `ratelimit:${clientId}`;
  const now = Date.now();
  const windowStart = now - windowSeconds * 1000;

  const pipe = redis.multi();
  pipe.zremrangebyscore(key, 0, windowStart);
  pipe.zadd(key, now, `${now}:${crypto.randomUUID()}`);
  pipe.zcard(key);
  pipe.expire(key, windowSeconds);

  const results = await pipe.exec();
  const count = results[2][1] as number;
  return count > limit;
}

Pub/Sub

const subscriber = redis.duplicate();
await subscriber.subscribe("notifications", "orders");

subscriber.on("message", (channel, message) => {
  const event = JSON.parse(message);
  switch (channel) {
    case "notifications":
      handleNotification(event);
      break;
    case "orders":
      handleOrderEvent(event);
      break;
  }
});

async function publishEvent(channel: string, event: object): Promise<void> {
  await redis.publish(channel, JSON.stringify(event));
}

Streams for Event Processing