Giving a Collaborator Access to One Site and MYSQL server Using His SSH Public Keys

I look up "SSH keys access to UserMIn" but found no results

I don't want to use Passwords. Is it possible to give a user access to

1) one server in Virtual Min (SFTP) 2) plus access to MySQl server

so that a) he has privileges to create a MYSQL data base, and manage it b) SFTP access the server.

Using his SSH public key, which I would be able to revoke if needed?

USE CASE: you have a Software developer in India. You would like to limit his "scope" and be able to revoke him any time. Passwords are vulnerable.