I thought we collectively learned this with stack overflows engineering blog years ago.

Scale vertically until you can't because you're unlikely to hit a limit and if you do you'll have enough money to pay someone else to solve it.

Docker is amazing development tooling but it makes for horrible production infrastructure.

Docker is great development tooling (still some rough edges, of course).

Docker Compose is good for running things on a single server as well.

Docker Swarm and Hashicorp Nomad are good for multi-server setups.

Kubernetes is... enterprise and I guess there's a scale where it makes sense. K3s and similar sort of fill the gap, but I guess it's a matter of what you know and prefer at that point.

Throw on Portainer on a server and the DX is pretty casual (when it works and doesn't have weird networking issues).

Of course, there's also other options for OCI containers, like Podman.

This is why there's an endless cycle of shitty SaaS with slow APIs and high downtime. People keep thinking that scale is something you can just add later.