Handling heavy load

Hi everyone.

I've got some questions regarding optimisation of a server to support more requests. I've recently launched an online game that's written in PHP and due to the current situation with everyone being stuck inside, it's been a lot more popular than we anticipated. I've been a hobbyist programmer for several years and this is the biggest project I've worked on so naturally, I had to learn fast about handling traffic. We're getting between 20-80 active users at any one time according to Google Analytics and are running Apache on a VPS with 4GB RAM and 3 vCPUs.

When we first launched, I was using Netdata to monitor everything and noticed that the Apache workers were being used up quickly and any subsequent requests were being timed out. We increased this from 24 (I think) to about 256 gradually until it was at a level that the server is comfortable. We still haven't gone over 100 but wanted to know that the option is there.

Is there anything else I can do to optimise the running? We're expecting a further influx of users each day as it's growing so want to be prepared. Is the answer simply increasing the server specs.

I apologise if some of what I say is irrelevant or naive - this is the first time I've made something like this and am generally still quite clueless.

Thanks a lot, any help is massively appreciated.

TLDR: launched PHP web app, server died, increased specs, server born again. Worried about 2nd death.

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