If avoiding downtime is your number one priority and you're willing to take on a lot of complexity to achieve it, then Kubernetes is probably the way to go. There are various chat platforms that can be distributed, but keeping a game server state synced between nodes isn't an easy task. There's a reason most multiplayer games are instanced.
I do find it a little odd that you're so concerned about uptime with a casual gaming server, but to each their own.