What should a new hire do in week one

Ship something tiny on day one, then read. The order matters: a merged one-line fix teaches the whole pipeline, and the codebase reads differently once you have touched it. A week of reading first produces a person who knows the architecture and cannot deploy.

It commits you to a format that is tedious to migrate away from later. The first weeks also look worse than doing nothing, which is when most people abandon it.