CDN and Edge Caching Strategy in 2026

CDN strategy is half-art half-math. The four axes break it down; the discipline is sustaining cache-hit-rate.

Why CDN matters

Without a CDN, the origin pays for every request. With a well-tuned CDN, the origin sees only the misses; the rest is absorbed at the edge.

• Origin offload. 80%+ of requests hit edge; origin sees a fraction; capacity goes 5x further.
• Latency win. Edge is geographically close to the user; round trips drop to single-digit milliseconds.
• Cost win. Egress through a CDN is cheaper than egress from a cloud origin at scale.
• DDoS absorption. CDNs absorb volumetric attacks at the edge; the origin never sees the spike.

Four strategy axes

• TTL: how long edge caches keep.
• Key: what makes a cache entry unique.
• Invalidation: how to purge stale.
• Vary: what request properties change the cached response.

CDN comparison

Each major CDN occupies a different niche. Pick by where your origins live, what features you need, and how much you are willing to pay.

• Cloudflare. Cheapest at scale, broad features, simple onboarding; the default for most teams.
• AWS CloudFront. Tight AWS integration; pairs well with S3, Lambda@Edge, ALB origins.
• Fastly. Fastest invalidation (sub-second), programmable edge via VCL; appeals to dynamic-heavy workloads.
• Akamai. Enterprise, expensive, mature; legacy in many large orgs and not always worth migrating away from.

Cache-hit target

Hit rate is the single metric that matters. Without a target, the CDN is decoration; with one, the discipline drives configuration choices.

• Static assets. 80%+ hit rate is the target; below this, the cache key or TTL is wrong.
• Dynamic content. 60% hit rate is achievable with careful key shape and short TTLs.
• Personalised content. 30% is realistic; per-user content kills cache hit rate by definition.
• Below target. Review TTL and key shape first; one of those is almost always the cause.

Antipatterns

• No CDN for static. Origin paid for every request.
• CDN with key including session. Hit-rate dies.
• No invalidation strategy. Stale content for hours.

What to do this week

Three moves. (1) Apply this pattern to your slowest production endpoint. (2) Measure p99 before/after. (3) Document the win and ship the runbook so the team can reproduce.