Caching & CDN Strategy Planner

Design effective caching at all layers.

Caching Layers

Client → CDN (Edge) → Server Cache → Database

CDN Configuration (CloudFront)

typescript
1const distribution = {
2  Origins: [
3    {
4      DomainName: "api.example.com",
5      CustomHeaders: [
6        {
7          HeaderName: "X-CDN-Secret",
8          HeaderValue: process.env.CDN_SECRET,
9        },
10      ],
11    },
12  ],
13  DefaultCacheBehavior: {
14    ViewerProtocolPolicy: "redirect-to-https",
15    AllowedMethods: ["GET", "HEAD", "OPTIONS"],
16    CachedMethods: ["GET", "HEAD"],
17    Compress: true,
18    DefaultTTL: 86400, // 1 day
19    MaxTTL: 31536000, // 1 year
20    MinTTL: 0,
21    ForwardedValues: {
22      QueryString: true,
23      Cookies: { Forward: "none" },
24      Headers: ["Accept", "Accept-Encoding"],
25    },
26  },
27  CacheBehaviors: [
28    {
29      PathPattern: "/api/static/*",
30      DefaultTTL: 31536000, // 1 year - never changes
31    },
32    {
33      PathPattern: "/api/dynamic/*",
34      DefaultTTL: 300, // 5 min - changes frequently
35    },
36  ],
37};

Server-side Caching (Redis)

typescript
1import Redis from 'ioredis';
2
3const redis = new Redis(process.env.REDIS_URL);
4
5async function getCachedOrFetch<T>(
6  key: string,
7  fetcher: () => Promise<T>,
8  ttl: number = 3600
9): Promise<T> {
10  // Try cache
11  const cached = await redis.get(key);
12  if (cached) {
13    return JSON.parse(cached);
14  }
15
16  // Fetch and cache
17  const data = await fetcher();
18  await redis.setex(key, ttl, JSON.stringify(data));
19
20  return data;
21}
22
23// Usage
24app.get('/api/user/:id', async (req, res) => {
25  const user = await getCachedOrFetch(
26    \`user:\${req.params.id}\`,
27    () => prisma.user.findUnique({ where: { id: req.params.id } }),
28    3600
29  );
30
31  res.json(user);
32});

Cache Invalidation

typescript
1// Invalidate on update
2app.put('/api/user/:id', async (req, res) => {
3  const user = await prisma.user.update({
4    where: { id: req.params.id },
5    data: req.body,
6  });
7
8  // Invalidate cache
9  await redis.del(\`user:\${req.params.id}\`);
10
11  // Invalidate CDN
12  await cloudfront.createInvalidation({
13    DistributionId: DISTRIBUTION_ID,
14    InvalidationBatch: {
15      Paths: { Items: [\`/api/user/\${req.params.id}\`] },
16      CallerReference: Date.now().toString(),
17    },
18  });
19
20  res.json(user);
21});

Cache Headers

typescript
1app.get("/api/products", (req, res) => {
2  res.set({
3    "Cache-Control": "public, max-age=3600", // Browser + CDN: 1h
4    ETag: generateETag(products),
5    "Last-Modified": new Date(products.updatedAt).toUTCString(),
6  });
7
8  res.json(products);
9});
10
11app.get("/api/user/profile", (req, res) => {
12  res.set({
13    "Cache-Control": "private, no-cache", // No caching (sensitive)
14  });
15
16  res.json(profile);
17});

Output Checklist

• CDN configured
• Server cache implemented
• Invalidation strategy
• Cache headers set
• Monitoring configured ENDFILE