What is the scale you are operating on? If you are having 10-50 servers and 5-10 people working on those - SSH keys are definitely good enough, it might be a b

What is the scale you are operating on? If you are having 10-50 servers and 5-10 people working on those - SSH keys are definitely good enough, it might be a bit of hassle to manage keys but quite OK. If you go into large corporation area with more than 100 servers and more than 50 tech people that need to login to those servers you probably would already found out that there are other options and you probably have to run your internal CA (certificate authority). If your org grows you would probably have CTO and other technical people who will have experience knowledge to implement things differently.