My approach is to learn the stack (read books, sketch/prototype). Get the team to whiteboard the architecture with you. This is better than existing documentat

My approach is to learn the stack (read books, sketch/prototype). Get the team to whiteboard the architecture with you. This is better than existing documentation because you will get the full commentary and start building a mental model of the software. Ask the team about problem areas. Don't push on major stack/architecture changes until you know the stack/architecture. Make sure the base engineering practices are there. You should have a seamless workflow from pre-merge code reviews, testing, and deploy.