I chose Digital Ocean server with redis db. There is no problem when 60 users are online.
A better replacement for redis
Pika is a persistent huge storage service , compatible with the vast majority of redis interfaces (details), including string, hash, list, zset, set and management interfaces. With the huge amount of data stored, redis may suffer for a capacity bottleneck, and pika was born for solving it. Except huge storage capacity, pika also support master-slave mode by slaveof command, including full and partial synchronization.