I'm using a spare laptop (Lenovo E570) running Ubuntu as a remote Docker host, and I do personal web dev on it - I run things like Flask / Django web apps (which are basically small, single-user HTTP servers), MongoDB, Redis, sometimes MySQL. I'd like to add paperless-ngx to all that, but that's a problem for later for later.
How do Raspberry Pi clusters stack up against spare laptops in terms of Docker performance? If I were to build one out, how many would I need to match the performance of my old laptop, if at all possible? I know people run Kubernetes on these things, but is K8S really necessary? Or can I just use straight Docker (maybe Docker Swarm)? What kinds of things are RPI clusters suited for?