Start reading the code. Ask "why" a lot - the code can tell you "what" and "how", but "why" isn't always there and is the most important piece of information. I

Start reading the code. Ask "why" a lot - the code can tell you "what" and "how", but "why" isn't always there and is the most important piece of information. If the codebase has been around for a while, this may also surface places where the reasoning no longer aligns with reality; these are great targets for refactoring. There's an interesting side-effect of this practice if you've got less-experienced devs on the team: it can encourage them to also ask more questions more confidently.