i am a mainly js engineer and so far have lived entirely within the firebase world as far as my backend goes. in your (and everyone else's) opinion, then: when -do- you need it? set some quantifiable bars for me please?
You don't need K8s, until you do, at which point switching can be a nightmare scenario.
If you need to do something that doesn’t map well to firebase, then my next stop would be AppEngine.
If what you want to run won’t map well to AppEngine, then start looking at K8S.
For me, this is usually wanting to run some kind of legacy system, or where a higher level of security is needed, or if you want or need to plan to run across multiple cloud vendors or in a mixed workload environment.
If AppEngine has been covered by google’s BAA when I started my current gig, I would have just used that, with k8s to handle the couple of oddball things that we are using that wouldn’t run as well there.
Personally, it’s not about scale so much as certain kinds of architectures or problems. You might have a system that needs to run a smallish number of nodes, but has reasons for needing what kubernetes offers without wanting to reinvent the wheel yet again with the existing cast of characters.
Firebase, AppEngine, etc. will all be blocked there?
Run your application on GKE and grow your company. When it comes time to move into China, add a cluster on a cloud provider there.
Really your next step in general is understanding containers and where they might be useful. K8s consideration is probably after that.