Content Delivery Networks Explained: CDN Caching, Edge...

In a nutshell: A CDN places content and sometimes application logic closer to users. It can reduce latency, absorb traffic spikes and improve resilience, but it only works well when caching rules, origin design and security controls are configured correctly.

What a CDN does

A content delivery network is a distributed platform of edge locations that sit between users and an origin server. When a user requests content, the CDN can serve cached files from a nearby edge or optimise the path back to the origin.

CDNs started with static content such as images, CSS, JavaScript and video. Modern CDNs also support dynamic acceleration, bot controls, WAF, DDoS mitigation, API protection and edge compute.

Caching and origin protection

Caching is controlled by HTTP headers, CDN rules and application behaviour. Public assets can be cached aggressively. Personalised pages, authenticated APIs and payment flows need more careful rules.

Origin shielding adds another layer: instead of every edge contacting your origin, the CDN funnels misses through a shield location. This can reduce origin load and improve cache efficiency.

Performance is more than cache hit ratio

A high cache hit ratio helps, but buyers should also look at time to first byte, TLS negotiation, image optimisation, HTTP/2 or HTTP/3 support, route quality, regional coverage and how quickly cache purges propagate.

For Singapore and APAC audiences, check actual edge presence and performance in the countries your users care about, not only global marketing maps.

Security services on CDNs

Many CDNs now sit at the security perimeter. They terminate TLS, filter malicious requests, enforce WAF rules, challenge bots, rate-limit APIs and absorb DDoS attacks before traffic reaches the origin.

This makes configuration critical. A CDN that protects the public hostname does not help if attackers can reach the origin directly through an exposed IP address.

CDN buyer checklist

Which content and API paths should be cached, bypassed or protected? Can the CDN cover your user geography with good latency? Are purge, versioning and rollback workflows documented? Is the origin locked down so only the CDN can reach it? Are WAF, DDoS, bot and API controls included or add-ons? Can reporting show cache hit ratio, origin load, errors and attack events?

Sources and further reading

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Content Delivery Networks Explained: CDN Caching, Edge and Security