Caching Strategies

Cache Patterns

Cache-Aside (Lazy Loading)

async function getUser(id: string): Promise<User> {
  // Check cache first
  const cached = await redis.get(`user:${id}`);
  if (cached) return JSON.parse(cached);

  // Cache miss - fetch from DB
  const user = await db.users.findById(id);

  // Store in cache
  await redis.setex(`user:${id}`, 3600, JSON.stringify(user));

  return user;
}

Write-Through

async function updateUser(id: string, data: Partial<User>) {
  // Update DB
  const user = await db.users.update(id, data);

  // Update cache
  await redis.setex(`user:${id}`, 3600, JSON.stringify(user));

  return user;
}

Write-Behind (Async)

async function updateUser(id: string, data: Partial<User>) {
  // Update cache immediately
  await redis.setex(`user:${id}`, 3600, JSON.stringify(data));

  // Queue DB update (async)
  await queue.add('updateUser', { id, data });

  return data;
}

Cache Invalidation

// Invalidate on update
async function deleteUser(id: string) {
  await db.users.delete(id);
  await redis.del(`user:${id}`);
}

// Pattern-based invalidation
await redis.del('users:*'); // Delete all user caches

HTTP Caching

// Cache-Control headers
res.set('Cache-Control', 'public, max-age=3600'); // Cache 1 hour
res.set('Cache-Control', 'private, no-cache');    // No caching
res.set('Cache-Control', 'public, max-age=31536000, immutable'); // Static assets

// ETag for conditional requests
const etag = generateETag(data);
res.set('ETag', etag);

if (req.headers['if-none-match'] === etag) {
  return res.status(304).end(); // Not Modified
}

Cache TTL Guidelines

Redis Data Structures

// String - Simple values
await redis.setex('key', 3600, 'value');

// Hash - Objects
await redis.hset('user:1', { name: 'John', email: 'john@example.com' });

// List - Queues
await redis.lpush('queue', 'item');

// Set - Unique values
await redis.sadd('tags', 'javascript', 'typescript');

// Sorted Set - Rankings
await redis.zadd('leaderboard', 100, 'player1');