Gergo, I want to thank you for leading the writeup of this. Having struggled with the scope boundaries for years, I know it's difficult work.
I'd like us to discuss an important scope boundary that this document doesn't cover: what is the proposed scope boundary between this team at the Wikimedia Services team? It would seem that "loosely coupled, well-documented components with clean interfaces and easy-to understand interactions" is exactly what @GWicke has proposed for years, but this document acknowledge potentially competing visions for describing how developers should interact with Wikimedia sites.
One thing that I was hoping would emerge from WikiDev16 is a working framework to address these issues collaboratively. Quoting WikiDev16, we had "Content access and APIs (T119029) - this is about getting our data in-and-out of the system (e.g. rest.wikimedia.org). The central problem in this area: 'how do we make accessing and distributing our data easier and more useful?'". Per T124504, I was hoping a working group would form in this area, but that doesn't seem to be happening.
My thinking behind the Availability proposal is to make the mandate a little clearer for a MediaWiki-focused team. That said, Ori has suggested combining Performance and Availability, which makes sense to me. A team focused on the stability and performance of MediaWiki would be a good counterbalance to desires for aggressive creation of loosely coupled microservices; there is only so aggressive one can get and still have an efficient, easy-to-understand system with respectable uptime.
Thoughts?