alt Hacker Newshow does git lock the repo on extreme concurrency? let's say 1000 devs writing to the same repository? eventually you'll have saturation of the resource locking everyone out.
When I've worked at big companies they had bespoke SCM that resolved this. But i'm curious about mid size teams that are big enough to overwhelm git but not so that they can rewrite it.
If those 1000 devs write to different branches then you only take a light lock on the branch, usually that is not the problem.
The problems start when there is a lot of changes on one branch and usually the first band-aid is to put a commit queue in place. The few very big companies that need even more than that probably aren't going to put their code on a new git hosting provider tomorrow.