At my current company we write a proposal for any new project/service (outlining 3 different paths for building a new service, or the option to "do nothing"). Then, once an async discussion happens on the google doc between the team and stakeholders, we settle on moving forward with one of the proposals (or "doing nothing"), and write a 10-20 page design doc outlining the entire service, architecture, etc. Then another round of async feedback between stakeholders on the proposal. Edits to the design doc are made based on feedback, and the design doc is then available for reference for anyone.

I really love this process, as a new member of the team I can go back and read the design doc for any of our systems and understand not only the architecture, but also why certain decisions were made. The caveat is that this a remote-first company with a strong asynchronous culture, which forces a lot of these discussions to take place in a google doc vs a conference room with no record.