Well, we have a dozen+ services running in a container platform and when (a) trying to present a uniform API to the outside world with versioning in the URL, (b) managing internal service discovery and (c) doing A-B testing + blue/green deployments, this gets tricky. Especially when you want to try and be event-driven and monitor service lifecycle events.

We could test out Kong, Consul, Fabio, and forget the event-driven callbacks; We could use Route 53 and ELBs; or we could just use Linkerd to drive this and get some pooling features and monitoring features as well.

I think of it as a layer both on top of the services and also a pool that the services swim around in and it ensures that there's one place to manage traffic, the services don't have to care how to do service discovery for other services and it's all being load balanced at a reasonable price.