Unfortunately I can't yet tell, as the corresponding code does not yet exist. Object and pack lookup is competitively fast so I would hope that translates well to everyday operations like that.

Actual numbers for what's there, pack access and traversal, can be found here: https://github.com/Byron/gitoxide/issues/1 and here: https://github.com/Byron/gitoxide/issues/5

That operation is much faster in recent versions of Git, especially after a GC or “git commit-graph write” command.