In Structured Logging for Node.js , I covered how to turn scattered console.log calls into structured, queryable events. That solves the "what happened in the system" problem. It does not solve a different, harder problem: proving what a specific user did to a specific piece of data, at a specific time, in a way that a customer's compliance team or your own support engineer can trust months later. That is what an audit log is for. This is part of the Full Stack SaaS Masterclass series, a...