Infrastructure

Systems

A web request crosses several boundaries before it reaches the application. Understanding each boundary makes troubleshooting a lot less mysterious.

DNS and routing

DNS maps a hostname to a destination. That answer can be cached at several points, so a changed record may not be visible to every client immediately. TTL values influence how long resolvers can keep an answer.

Routing determines which network path is used after resolution. A successful DNS response does not guarantee that the destination is reachable.

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HTTPS and certificate management

TLS provides an authenticated encrypted connection. A certificate must cover the requested hostname and be valid at the time of the handshake.

Automated renewal is useful, but renewal and deployment are separate operations. A service may need to reload its configuration before it presents a renewed certificate.

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Origin and edge

The origin holds the authoritative content. An edge cache may respond to repeat requests closer to the visitor, depending on cache rules, content type and request headers.