I think it depends on number of factors:
- How decoupled is the service? If a particular service doesn’t share code base with rest of the app and also needs a separate server to run then moving to a separate Repo is a good choice.
- Number of team members is also a big factor. If the team is small (under approx 25 developers), I will suggest going with a mono Repo as in such case mostly developers tend to work with lot of services instead of one service per developer concept (generally happens in large teams). Mono Repo makes the work easier and increases the speed of development a lot in small teams.
Being a full stack developer, I make a lot of jump in code so keeping it in one place helps a lot but if a service is totally decoupled and requires a separate server (it should if it decoupled) then only I choose to move it to separate Repo.