I generally want an idea of the data model and data flow before starting to code. Define components with responsibilities, but leave their interfaces pretty abs

I generally want an idea of the data model and data flow before starting to code. Define components with responsibilities, but leave their interfaces pretty abstract, other than being able to fit check that all the right information will be available. Choosing async vs sync responses fits into that as well. For situations with a lot of breadth in possible approaches or a lot of edge cases, I like to have a reviewed design ahead of time. That or if I'm going to get a lot of people to work on it at the same time. For that, without pretty clear interfaces, everyone gets bottlenecked trying to make clashing updates to the interfaces