How can we reclaim disk space, rebuild indexes, or compact an M0 Shared instance?

Hello!

I don’t think so… You must keep in mind that a M0 Shared Instance is so limitated, not only in hardware aspects, but also in administration.

I have found other discussion that can help you to answer your question: How to get fragmentation stats in mongo/wiredtiger mongo version 4.4

I hope i have help you with this link. If you have any doubts, please let me know them.