At my wits end with this. Hosted content moving fine with caching, but everything inside wp-admin while editing posts/page takes FOREVER to save - between 20-30s per post.

Facts/steps:

• Website is busy'ish (7-15k visitors and 130k'ish requests a day)
• Everything is fronted by cloudflare.
• Origin is on a dedicated VPS with 25% ram utilization and 10% CPU utilization (up to 20% at highest spike).
• VPS is "wp optimized" and has the following 'managed services' Apache, Imunify360, Memcached, MySQL, NGINX, phpfpm, Redis, Varnish that are running.
• Web/DB on same box, so network throughput/connectivity/latency is eliminated.
• Tested with all plugins being disabled, doesn't change things.

Everything i've been researching says slow API, usually due to plugins, but i've eliminated that as a contributor, plus we don't use a lot of plugins.

FWIW: I restored to a local dev server and the problem seems to be less; HOWEVER, the local box is an i9-14th gen with 128gb of memory, so i think i'm masking the problem by throwing a shitload of power at it.