You can use it for web apps/services (https://mesosphere.com/docs/getting-started/service-discover...). But I'm with you on databases. I guess I just like knowing that those hosts are being managed and cared for (pets vs. cattle).

With that said, I often wonder how many people are using Mesos/Marathon before they have any need for it? Using it on for 4 hosts vs. 40 or 400?

There's nothing wrong with Mesos on 4 hosts, though...

Anything more than a single host requires additional co-ordination - picking Mesos is mostly no different than rolling alternate methods for doing so.

It's not choice with the least overhead, but it's a possibility, for those for whom it has the right conveniences...

Yeah i have seen Mesos used for managing big data frameworks like Spark. Any large distributed computing framework has to deal with some of the same problems - managing resources on worker nodes, sending tasks, getting results, scheduling etc. and Mesos/YARN provide a common base here, better than each framework duplicating the same code and solving the same problems.

That makes sense, thanks. The workers are pretty independent from each other, too, so this setup would be more fitting for that.