A simple file based caching plugin like KeyCdn Cache Enabler saves every page as static html and uses Apache rewrite rules to serve those files until invalidated, bypassing php entirely. It is trivially easy to install and configure.
Free tier cloudflare caching basically does the same, host your dns on cloudflare, turn CDN on for a record, and whatever users request from that IP gets cached statically, distributed across and served by Cloudflare’s global cdn.
For more interactive database heavy applications like ecommerce you can go deeper with opcode and object caching, but none of it is that complicated. There are plenty of managed solutions that do all of this for you.
Free tier cloudflare caching basically does the same, host your dns on cloudflare, turn CDN on for a record, and whatever users request from that IP gets cached statically, distributed across and served by Cloudflare’s global cdn.
For more interactive database heavy applications like ecommerce you can go deeper with opcode and object caching, but none of it is that complicated. There are plenty of managed solutions that do all of this for you.