A cloud API is unreachable. Where do I start?

Definition:

An unreachable cloud API may fail before the request reaches application code. DNS, TLS, routing, firewall rules, load-balancer health and listening ports are separate layers to verify. Checking them in order avoids opening broad access or restarting healthy services without evidence.

Key points:

• Check DNS resolution, TLS, load-balancer health and application logs.

• Check routes, security groups/firewall rules and listening ports.

• Open only the required access; do not expose the database publicly as a shortcut.

• Compare a request from inside the service network with one from outside to narrow the failing boundary.

Interview point:

• State where the request stops and what measurement proves it before proposing a network rule change.