What to do, especially when you don’t know the domain and the tech stack?
Building trust is tricky, but you might have an advantage. If you don’t know the tech stack and the domain very well, you should not give suggestions immediately. You should ask questions as an outsider. This can make them realize things they didn’t consider before. It will help you to understand the domain without being biased and build trust. When you ask questions, they will see that you care. While asking, admit that you don’t know and are trying to learn. This behavior can lower their shield.
