I'm glad you moved away from AWS, I wouldn't even consider going for VM hosting and would've gone dedicated from the get go (or even self-hosting on a colo / using a good fiber connection at home, but I guess I live in a super privileged country when it comes to ISPs).
Isn't k8s a bit overkill tho? Front-loaded caching seems to make sense, but a single 10gbit dedi could probably resolve the issue easier and simpler, couldn't it?
Just to add some more background on this: I used to work tightly with the Network Team in the website team of the biggest contender in its market (can't disclose which one without people figuring out the company since the market is a bit niche).
We had 20'000 Users a day with a lot of images served.
The whole infrastructure consisted of 2 Firewall servers and the main DB (pSQL) on 2 self-hosted servers (think colo, it was sitting in a very remote location with 2 big diesel generators that would've ran the whole datacenter for a week iirc), with 14 Hetzner backend mirrors who ran the whole PHP code, served images and the angular + some weird custom Javascript. Scaling was done by simply throwing more Hetzners at it.
Given that Lemmy runs super performance efficient in comparison to 20 year deprecated PHP code that held together with ducttape, I feel like much less could make it work.