High CPU usage when using parse-server with clusters

I am using latest version of parse-server(2.3.8) for my slots casino app and app is comunicating to server frequently just like real time game. My server configuaration is - DB Server - Mongo Atlas(M30 - 8GB RAM, 40GB storage) Parse Server - Rackspace(15GB RAM, 50GB Storage, 8 Core)

For multithread support i am using clustering using pm2(latest version). I am using 6 core from 8 for clustering. Currently there is max 10-20 Concurrent users. Initial when i startup the parse server using clustering - pm2 start main.js -i 6 The cpu usage us max 2% - 5%. After 1 day the cpu usage becomes 70% - 90% while the concurrent users are 10-20 or less.

Please help me how to minimize the cpu usage, where i am going wrong.

via MD Zakir