I like the usage of monorepos as well but wanted to point out for the “store everything in one repo” crowd that Google has their own DVCS and lots of tooling for it. They can (aka have no other choice than to) checkout slices since the full repo is too large for a single machine and the data is stored in their Big Data infrastructure. They also have user permissions for subtrees which Git doesn’t by design. They also have tooling for sweeping changes over large parts of the repo as well as rollback etc. I’ve read that their deployment pipelines always point to the latest master of their libraries so everybody is pretty careful not to check in broken builds whose tests are greeen 
. Git or your git repo host may also have problems with huge repos in the long run since it wasn’t designed for that use case, BitBucket seems to have that at least and GitHub has a soft limit of 1GB, Facebook also struggled.