Use AuthorizedKeysCommand in docker builds
Summary
Since you're in control of the versions/etc - seems like very little reason to not use this by default in the docker based builds.
Proposal
Use the faster ssh key lookup with AuthorizedKeysCommand in docker based builds for better performance/scaling. Since all of the files/content related to this are managed - this should be something that could be added transparently to the container builds.
References
https://gitlab.com/help/administration/operations/fast_ssh_key_lookup