Re: GitLab the incompetent startup, relying on their free-tier (slurping) Azure Cloud
Eh, the primary problem here is Postgres, presume you ignore that since its OSS and can do no wrong.
GitLab have long moved off Azure as they had a large IOPS requirement (200000) that didn't match what Azure could provide. They admit they didn't do the basic math before moving onto it so it was always going to fail.
Use the best cloud for your use cases if you can. If you have massive IOPS requirements the cloud might not be for you, writes will be slower as it has to be replicated across zones, reads will have limits as there are other people in your cloud as well.
The reason they have huge IOPS is Git, 300 reads for every 10 writes, its massively inefficient at scale. Again don't mention that since its OSS and can do no wrong.
MS have created a virtual layer to fix this problem for large repositories https://gvfs.io/
No your anecdotal story about your use case does not mean it applies to larger use cases, just because you can walk to the shops does not mean you can run a ultra marathon, unless its an Open Source marathon of course.
GitLab is an old skool architecture where they are just renting servers, that will bring its own pain.
I like Go its a nice language to work with. OOS is not bad, neither is proprietary, its whatever you need to get the job done.