Caching Strategies
Speed up your app with smart caching at every layer.
When to Use This Skill
- Slow database queries
- Expensive computations
- External API responses
- Session data
- Frequently accessed data
Cache Layers
┌─────────────────────────────────────────────────────┐
│ Request │
└─────────────────────────────────────────────────────┘
│
▼
┌─────────────────────────────────────────────────────┐
│ Layer 1: HTTP Cache (CDN/Browser) │
│ - Static assets, public API responses │
│ - Cache-Control headers │
└─────────────────────────────────────────────────────┘
│ miss
▼
┌─────────────────────────────────────────────────────┐
│ Layer 2: In-Memory Cache (Node/Process) │
│ - Hot data, computed values │
│ - LRU eviction │
└─────────────────────────────────────────────────────┘
│ miss
▼
┌─────────────────────────────────────────────────────┐
│ Layer 3: Distributed Cache (Redis) │
│ - Shared across instances │
│ - Session data, rate limits │
└─────────────────────────────────────────────────────┘
│ miss
▼
┌─────────────────────────────────────────────────────┐
│ Layer 4: Database │
└─────────────────────────────────────────────────────┘TypeScript Implementation
Multi-Layer Cache
// cache.ts
import { Redis } from 'ioredis';
import { LRUCache } from 'lru-cache';
interface CacheOptions {
ttl?: number; // Time to live in seconds
staleWhileRevalidate?: number;
tags?: string[]; // For invalidation
}
class MultiLayerCache {
private memory: LRUCache<string, { value: unknown; expires: number }>;
private redis: Redis;
constructor(redis: Redis) {
this.redis = redis;
this.memory = new LRUCache({
max: 1000,
ttl: 60 * 1000, // 1 minute default
});
}
async get<T>(key: string): Promise<T | null> {
// Layer 1: Memory
const memoryHit = this.memory.get(key);
if (memoryHit && memoryHit.expires > Date.now()) {
return memoryHit.value as T;
}
// Layer 2: Redis
const redisValue = await this.redis.get(key);
if (redisValue) {
const parsed = JSON.parse(redisValue) as T;
// Populate memory cache
this.memory.set(key, { value: parsed, expires: Date.now() + 60000 });
return parsed;
}
return null;
}
async set<T>(key: string, value: T, options: CacheOptions = {}): Promise<void> {
const ttl = options.ttl || 3600; // 1 hour default
// Set in Redis
await this.redis.setex(key, ttl, JSON.stringify(value));
// Set in memory (shorter TTL)
this.memory.set(key, {
value,
expires: Date.now() + Math.min(ttl * 1000, 60000),
});
// Track tags for invalidation
if (options.tags) {
for (const tag of options.tags) {
await this.redis.sadd(`cache:tag:${tag}`, key);
}
}
}
async getOrSet<T>(
key: string,
fetcher: () => Promise<T>,
options: CacheOptions = {}
): Promise<T> {
const cached = await this.get<T>(key);
if (cached !== null) {
return cached;
}
// Prevent cache stampede with lock
const lockKey = `lock:${key}`;
const acquired = await this.redis.set(lockKey, '1', 'EX', 10, 'NX');
if (!acquired) {
// Another process is fetching, wait and retry
await new Promise(resolve => setTimeout(resolve, 100));
return this.getOrSet(key, fetcher, options);
}
try {
const value = await fetcher();
await this.set(key, value, options);
return value;
} finally {
await this.redis.del(lockKey);
}
}
async invalidate(key: string): Promise<void> {
this.memory.delete(key);
await this.redis.del(key);
}
async invalidateByTag(tag: string): Promise<void> {
const keys = await this.redis.smembers(`cache:tag:${tag}`);
if (keys.length > 0) {
await this.redis.del(...keys);
for (const key of keys) {
this.memory.delete(key);
}
}
await this.redis.del(`cache:tag:${tag}`);
}
}
export { MultiLayerCache, CacheOptions };Cache-Aside Pattern
// user-service.ts
class UserService {
constructor(private cache: MultiLayerCache) {}
async getUser(id: string): Promise<User> {
return this.cache.getOrSet(
`user:${id}`,
async () => {
return db.users.findUnique({ where: { id } });
},
{ ttl: 3600, tags: ['users', `user:${id}`] }
);
}
async updateUser(id: string, data: Partial<User>): Promise<User> {
const user = await db.users.update({
where: { id },
data,
});
// Invalidate cache
await this.cache.invalidate(`user:${id}`);
return user;
}
async deleteUser(id: string): Promise<void> {
await db.users.delete({ where: { id } });
await this.cache.invalidateByTag(`user:${id}`);
}
}HTTP Caching Middleware
// http-cache-middleware.ts
import { Request, Response, NextFunction } from 'express';
interface HttpCacheOptions {
maxAge?: number;
sMaxAge?: number;
staleWhileRevalidate?: number;
private?: boolean;
vary?: string[];
}
function httpCache(options: HttpCacheOptions = {}) {
return (req: Request, res: Response, next: NextFunction) => {
const directives: string[] = [];
if (options.private) {
directives.push('private');
} else {
directives.push('public');
}
if (options.maxAge !== undefined) {
directives.push(`max-age=${options.maxAge}`);
}
if (options.sMaxAge !== undefined) {
directives.push(`s-maxage=${options.sMaxAge}`);
}
if (options.staleWhileRevalidate !== undefined) {
directives.push(`stale-while-revalidate=${options.staleWhileRevalidate}`);
}
res.setHeader('Cache-Control', directives.join(', '));
if (options.vary) {
res.setHeader('Vary', options.vary.join(', '));
}
next();
};
}
// Usage
app.get('/api/products',
httpCache({ maxAge: 60, sMaxAge: 300, staleWhileRevalidate: 86400 }),
async (req, res) => {
const products = await getProducts();
res.json(products);
}
);Python Implementation
# cache.py
import json
import time
from typing import TypeVar, Callable, Optional
from functools import lru_cache
import redis
T = TypeVar('T')
class MultiLayerCache:
def __init__(self, redis_client: redis.Redis):
self.redis = redis_client
self._memory: dict[str, tuple[any, float]] = {}
def get(self, key: str) -> Optional[any]:
# Layer 1: Memory
if key in self._memory:
value, expires = self._memory[key]
if expires > time.time():
return value
del self._memory[key]
# Layer 2: Redis
redis_value = self.redis.get(key)
if redis_value:
parsed = json.loads(redis_value)
self._memory[key] = (parsed, time.time() + 60)
return parsed
return None
def set(self, key: str, value: any, ttl: int = 3600, tags: list[str] = None):
self.redis.setex(key, ttl, json.dumps(value))
self._memory[key] = (value, time.time() + min(ttl, 60))
if tags:
for tag in tags:
self.redis.sadd(f"cache:tag:{tag}", key)
async def get_or_set(
self,
key: str,
fetcher: Callable[[], T],
ttl: int = 3600,
) -> T:
cached = self.get(key)
if cached is not None:
return cached
# Simple lock for stampede prevention
lock_key = f"lock:{key}"
if not self.redis.set(lock_key, "1", ex=10, nx=True):
await asyncio.sleep(0.1)
return await self.get_or_set(key, fetcher, ttl)
try:
value = await fetcher()
self.set(key, value, ttl)
return value
finally:
self.redis.delete(lock_key)
def invalidate_by_tag(self, tag: str):
keys = self.redis.smembers(f"cache:tag:{tag}")
if keys:
self.redis.delete(*keys)
for key in keys:
self._memory.pop(key.decode(), None)
self.redis.delete(f"cache:tag:{tag}")Decorator Pattern
# cache_decorator.py
from functools import wraps
def cached(key_template: str, ttl: int = 3600, tags: list[str] = None):
def decorator(func):
@wraps(func)
async def wrapper(*args, **kwargs):
# Build cache key from template
key = key_template.format(*args, **kwargs)
cached_value = cache.get(key)
if cached_value is not None:
return cached_value
result = await func(*args, **kwargs)
cache.set(key, result, ttl=ttl, tags=tags)
return result
return wrapper
return decorator
# Usage
@cached("user:{user_id}", ttl=3600, tags=["users"])
async def get_user(user_id: str) -> User:
return await db.users.find_unique(where={"id": user_id})Cache Invalidation Strategies
1. Time-Based (TTL)
await cache.set('key', value, { ttl: 3600 }); // Expires in 1 hour2. Event-Based
// On data change
eventBus.on('user.updated', async (userId) => {
await cache.invalidate(`user:${userId}`);
});3. Tag-Based
// Set with tags
await cache.set(`product:${id}`, product, { tags: ['products', `category:${categoryId}`] });
// Invalidate all products in category
await cache.invalidateByTag(`category:${categoryId}`);4. Write-Through
async function updateUser(id: string, data: Partial<User>) {
const user = await db.users.update({ where: { id }, data });
await cache.set(`user:${id}`, user); // Update cache immediately
return user;
}Best Practices
- Cache at the right layer - Don't cache everything in Redis
- Use appropriate TTLs - Balance freshness vs performance
- Prevent stampedes - Use locks or stale-while-revalidate
- Monitor hit rates - Track cache effectiveness
- Plan for invalidation - Use tags for related data
Common Mistakes
- Caching user-specific data without proper keys
- No cache invalidation strategy
- TTLs too long (stale data) or too short (no benefit)
- Caching errors or null values
- Not handling cache failures gracefully