Most likely, yes. It’s just a dedicated server with specific tunings. Like jwatte said, the only things that really need to go into a database are cross-zone information, like player stats (like health, xp, mp, inventory, equipments, buffs, etc). Things that change inside a zone (enemy position and state, for example) can exist only in the server, so you can prototype that with only UE4.
You’ll also need to work a lot in the network replication of player and enemies to allow a good amount of players per zone. That often involves adapting the game design so the gameplay takes those things in account.
Since you seem to be at the very beginning and don’t have experience with this, I suggest you start working on a simple prototype where you have a dedicated server where people can connect to and move from there. Avoid doing a billion things at once, you’ll have problems getting anywhere that way.