Caching & CDN Strategy Planner

Design effective caching at all layers.

Caching Layers

Client → CDN (Edge) → Server Cache → Database

CDN Configuration (CloudFront)

const distribution = { Origins: [ { DomainName: "api.example.com", CustomHeaders: [ { HeaderName: "X-CDN-Secret", HeaderValue: process.env.CDN_SECRET, }, ], }, ], DefaultCacheBehavior: { ViewerProtocolPolicy: "redirect-to-https", AllowedMethods: ["GET", "HEAD", "OPTIONS"], CachedMethods: ["GET", "HEAD"], Compress: true, DefaultTTL: 86400, // 1 day MaxTTL: 31536000, // 1 year MinTTL: 0, ForwardedValues: { QueryString: true, Cookies: { Forward: "none" }, Headers: ["Accept", "Accept-Encoding"], }, }, CacheBehaviors: [ { PathPattern: "/api/static/", DefaultTTL: 31536000, // 1 year - never changes }, { PathPattern: "/api/dynamic/", DefaultTTL: 300, // 5 min - changes frequently }, ], };

Server-side Caching (Redis)

import Redis from 'ioredis';

const redis = new Redis(process.env.REDIS_URL);

async function getCachedOrFetch<T>( key: string, fetcher: () => Promise<T>, ttl: number = 3600 ): Promise<T> { // Try cache const cached = await redis.get(key); if (cached) { return JSON.parse(cached); }

// Fetch and cache const data = await fetcher(); await redis.setex(key, ttl, JSON.stringify(data));

return data; }

// Usage app.get('/api/user/:id', async (req, res) => { const user = await getCachedOrFetch( `user:${req.params.id}`, () => prisma.user.findUnique({ where: { id: req.params.id } }), 3600 );

res.json(user); });

Cache Invalidation

// Invalidate on update app.put('/api/user/:id', async (req, res) => { const user = await prisma.user.update({ where: { id: req.params.id }, data: req.body, });

// Invalidate cache await redis.del(`user:${req.params.id}`);

// Invalidate CDN await cloudfront.createInvalidation({ DistributionId: DISTRIBUTION_ID, InvalidationBatch: { Paths: { Items: [`/api/user/${req.params.id}`] }, CallerReference: Date.now().toString(), }, });

res.json(user); });

Cache Headers

app.get("/api/products", (req, res) => { res.set({ "Cache-Control": "public, max-age=3600", // Browser + CDN: 1h ETag: generateETag(products), "Last-Modified": new Date(products.updatedAt).toUTCString(), });

res.json(products); });

app.get("/api/user/profile", (req, res) => { res.set({ "Cache-Control": "private, no-cache", // No caching (sensitive) });

res.json(profile); });

Output Checklist

• CDN configured

• Server cache implemented

• Invalidation strategy

• Cache headers set

• Monitoring configured ENDFILE