> what are the major areas where you face performance issues? > Does the choice of RoR play a part in performance problems?
RoR does not play a part in the performance problems as much as any other language choice. Our performance problems come from at least 3 different fronts: lack of caching in some specific points making us call the same complex/slow operations many times, NFS (filesystem) performance as a whole, and algorithms that worked really well at small scale, but not anymore, both at app level and at DB level.
I think that RoR is a really good option for building a product fact, and eventually it is necessary to start specializing specific parts that do not perform anymore, and just replacing what cannot be specialized. The key element here is that we need to measure first to see where the problem is.
> Can performance be improved by deploying more servers?
Not really, more front end servers means more load on the NFS backend, so there is no easy solution here. The first step into fixing this issue right now is this one: https://gitlab.com/gitlab-com/infrastructure/issues/139 and then we will start playing with a distributed FS as a longer term solution: https://gitlab.com/gitlab-com/operations/issues/1
As a final note, we are using some specific issues to measure performance as a blackbox, and those issues are seeing some really good progress lately. So stay tuned :)