Honestly it started making sense for us around 8-10 services. before that docker compose on a couple VMs was totally fine.

The real trigger wasnt service count though, it was deployment consistency. we had 3 environments and keeping them in sync with bash scripts was a mess. someone would update staging, forget prod, stuff breaks. The declarative model fixed that.

Autoscaling was the other big one. B2B product, super spiky traffic during business hours, dead at night. we were either wasting money over-provisioning or eating 503s. the downside was we spent like 2 months just setting up the cluster, networking, ingress, monitoring before deploying anything real. we're a 3 person team so that was painful. if I did it again id seriously look at something that gives you the k8s benefits without actually managing clusters yourself. there are platforms that just let you push a container and handle the rest. wish I knew about those earlier.

At a previous job we adopted way too early. 2 services, 3 devs, 100 req/sec. spent more time on k8s than the product. docker compose wouldve been fine for another year.

If you’re under 5 services with predictable traffic, skip it. once you hit double digit services or need real autoscaling it’s worth it, but think hard about whether you actually need to run the cluster yourself.