Logging

Logging is how you see what your system did after the fact, without a debugger attached. It's the difference between resolving an incident in minutes and staring at a stack trace wishing you'd logged more.

The natural instinct is to treat logging as an afterthought — bolt it onto error handlers, rank it last in code review fix lists, add it "later." That instinct is wrong. Logging is a first-class design concern. Build it into the normal flow of the code, not just the failure path.

Match the user's language. If no language is specified or implied, use Python.

Log the happy path, not just errors

The biggest gap in most logging: every error branch has a log line, but successful operations are silent. When investigating an incident, you need to see what the system did, not just what broke. If only failures are visible in logs, you can't distinguish "no traffic" from "everything worked fine."

Log the outcome of each significant operation — request handled, job completed, payment processed. One INFO line per significant operation on the happy path.