CDN testing overview

CDNs are the invisible performance layer between your users and your origin. When they work correctly, cached assets arrive from a nearby edge node in milliseconds and your origin is barely touched. When they don’t — after a purge storm, a cache-key misconfiguration, or an unexpected cache miss at peak traffic — origin servers bear the full load of millions of concurrent requests, latency climbs, and errors cascade. CDN testing makes these failure modes visible before they happen in production.

What CDN testing covers

CDN testing is not a single test type. It is a collection of techniques that together verify:

• Cache correctness — are the right responses being cached, for the right duration, with the right scope?
• Origin protection — does the CDN actually reduce load on your origin, and does it hold up when the cache is cold?
• Edge performance — are users in each geography receiving responses from a nearby edge node, and does latency reflect that proximity?
• Purge and invalidation behaviour — when you purge a cached resource, what happens to the sudden origin traffic surge?
• Cache-key accuracy — are requests that should share a cached copy sharing one, and are requests that must not share a cached copy correctly isolated?

MaxoPerf’s role in CDN testing

MaxoPerf tests CDN infrastructure the same way it tests any other HTTP endpoint: by generating realistic load from cloud load locations spread across regions, asserting on response headers, and surfacing TTFB and latency percentiles in a rich results dashboard. The key advantages for CDN testing are:

• Multi-region runners — generate load simultaneously from multiple geographic locations so each region’s edge performance is measured independently.
• Header assertions — assert on Cache-Control, Age, X-Cache, and any CDN-specific response headers directly in your test scripts.
• TTFB measurement — the run overview captures Time to First Byte, the metric most sensitive to cache hit/miss state.
• Per-endpoint breakdown — label requests by URL pattern or asset type to compare latency across resource categories.
• Failure criteria — set p95 TTFB and error-rate thresholds that automatically fail a run if edge performance degrades.

Section map

Use this table to find the right page for your situation.

You want to…	Go to
Validate that responses are being cached and measure hit ratio	Cache hit/miss testing
Test what happens when cached content is purged or invalidated	Cache invalidation and purge testing
Verify origin protection and measure how much traffic the CDN absorbs	Origin shield and offload testing
Measure per-region edge latency from multiple locations simultaneously	Multi-region edge performance
Measure TTFB, large-asset delivery, compression, and HTTP/2	TTFB and asset delivery
Understand cache-key composition, Vary headers, and cache poisoning risks	Cache key and Vary testing
Find ready-made scenarios for common CDN situations	Day-to-day CDN scenarios
Review do/don’t rules before running any CDN test	CDN testing do and don’t

Reading order

If this is your first time testing CDN infrastructure, read in this order:

1. Cache hit/miss testing — understand the fundamentals of cache state and how to measure it.
2. TTFB and asset delivery — learn which metrics matter for CDN performance.
3. Multi-region edge performance — run your first geo-distributed CDN test in MaxoPerf.
4. Origin shield and offload testing — verify origin protection under realistic load.
5. Cache invalidation and purge testing — test the riskiest CDN operation.
6. Cache key and Vary testing — validate cache-key logic and Vary header handling.
7. Day-to-day CDN scenarios — apply everything to real-world situations.
8. CDN testing do and don’t — final rules before running in production.

Before you start

• You need a MaxoPerf workspace with access to at least two cloud load locations to exercise multi-region edge behaviour.
• Confirm you are authorized to generate load against the CDN endpoint. Most CDN providers permit load testing on customer-owned origins with prior notice — check your provider’s terms. See CDN testing do and don’t for details.
• Run a smoke test against your CDN URL first to confirm basic reachability and check which headers the CDN returns.
• Read HTTP and REST load testing if you are new to writing HTTP test scripts in MaxoPerf.

Where to go next

• Cache hit/miss testing — start with the fundamentals.
• Multi-region edge performance — run your first geo-distributed CDN test.
• Cookbook: multi-region distributed load — the general multi-region recipe this section builds on.