Managing Multiple SSH Keys Across Multiple Servers

Not strictly Laravel related, so I hope it's fine.

I'm currently on a dev team consisting of around 15 developers. Additionally, we regularly have co-op students cycle in and out over time. We have roughly 250 separate Digital Ocean droplets for various projects, both internal and external.

A very, very common issue we encounter is that a given developer doesn't have SSH access to a given droplet. Some of these droplets date back over four years (in other words, they've been here longer than most of the actual devs at this point). It's not at all uncommon for a droplet to only have an SSH key for one dev.

What this results in is a frequent scramble to find out who has access, who can add an SSH key, etc. when an issue crops up on an older droplet.

I'd like to minimize this situation if I can, while still maintaining the use of SSH keys as out authentication method.

Obviously there is a level of management to be done here, but it's simply not practical, however 'process-driven' it might be, to add or remove a dev's SSH key from 250 servers when the need arises.

So the essence of my question: has anyone found or used a good solution for central SSH key management across multiple servers? An ideal situation would be an interface that an admin could access, allowing them to enable/disable SSH keys for specific connected servers.