I haven't ran into a good use-case to try out server-less yet. Either cold starts would be a problem (for example, I have an endpoint that needs to load a 5GB model into RAM, and it takes about 45 seconds). Or, it's just much more expensive than a VPS if the service is projected to constantly serve many requests all day. Containerized services on a VPS doesn't require much server maintenance (unless you have a dozen or so micro-services, then yeah, Kubernetes maintenance adds a lot of overhead).