Can two servers connect to the same AWS CodeCommit repository?

Yes, any number of servers or computers can clone a AWS CodeCommit repo. Since CodeCommit uses Git and Git is a distributed revision control system, it means that each clone is a complete copy of the Git database. If you and your team are trying to commit conflicting changes to a file in the same branch on CodeCommit, whoever is trying to make the last commit will need to reconcile those conflicts before Git will allow the commit to happen.

Here are our docs on connecting to a Git repo in AWS CodeCommit https://docs.aws.amazon.com/codecommit/latest/userguide/how-to-connect.html

Here are the basics of how merging works in Git - https://git-scm.com/book/en/v2/Git-Branching-Basic-Branching-and-Merging