Most people responding here are nitpicking on whether SO’s architecture is the one. I wasn’t trying to imply that at all.

I wanted to drive a point and SO is a good enough example to show that a massive company of the size of SO can run, so can your tiny app.

Don’t scale prematurely. A lot can be done by reasonable vertical scaling.

For one $120k/year Kubernetes infra engineer, you could pay for entire rack of beefy servers.

Obviously YMMV. Discussion about SO and licensing details are distracting.