Routing & Handlers
How a method and a path become a function call, how precedence resolves ambiguity, and what a handler should and should not be responsible for.
A route table is a lookup structure over method and path; everything else about routing follows from which structure your framework chose.
A path parameter is an attacker-supplied string that happens to be positioned where you expected an identifier.
The least standardised part of an HTTP request, parsed differently by every stack, and the usual entry point for unbounded work.
When two routes can match one path, something decides which wins — and in half of all frameworks that something is the order of lines in a file.
API Design decides the versioning policy; this is what the policy costs inside a running process, and how to pay it without forking the codebase.
A handler is an adapter between HTTP and one application operation — parse, resolve caller, call, map, return — and everything else it does belongs somewhere it can be reused and tested.