We have a project where we have huge amount (>100k) of users in the system. With that amount of users it's pointless to start listing them all from UX and performance point of view. Typical use cases are to search for an individual user or to browse users by groups. What would be the optimal way of doing this? Just providing a search bar might leave the UI too empty looking.
Just providing a search bar might leave the UI too empty looking.
The alternative is cluttering the interface with needless things. If you can keep it simple and self-explanatory, do so.
But if you haven't done so already, interview the users of the system to see what criteria they most often search by. In a database of 100k people I think it's unlikely that they'll only want to search by name and group.
And do them a minor favour by having auto-complete suggestion with sections by forename and by surname, like this (poorly constructed) wireframe: