At certain times my server gets pretty slow. But RAM and CPU are fine!

May 25, 2018 1.4k views
Apache MySQL MariaDB PHP Ubuntu 16.04

I installed a server with LAMP recently, then I put my entire website and database to the droplet, and finally installed Let`s Encrypt.
Everything is working very well. But, when I post in my site, and notify to my app in Android/iOS, the server gets very slow! I think is a lot of access.
I’ve tried to optimize the SQL consults.
I switched Apache Prefork to Apache Event with FastCGI and PHP7-FPM.
I moved to MariaDB.

And the server stays very slow, but the CPU and RAM are very fine! Look Here:
I need help please! I don`t know what to do now!

I’m running Ubuntu 16.04 server with 4GB RAM, 80GB Disk, and NYC1. Thanks!