Have you looked at the etcd keys and values in a Kubernetes cluster? It's a _remarkably_ simple schema you could do in pretty much any database with fast prefix or path scans.
https://github.com/k3s-io/kine is a reasonably adequate substitute for etcd. sqlite, MySQL, PostgreSQL can also be substituted in. Etcd is from the ground up built to be more scale-out reliable, and that rocks to have baked in. But given how easy it is to substitute etcd out, I feel like we are at least a little off if we're trying to say "etcd is also the entire point of k8s" (the APIserver is)
Ideally, i'd love to see a database specific offering. Use postgres async replication (ideally somehow sharded so there's not a single consumer node) to some fan out system that's doing all the watching.
But etcd mostly does the job, seems unlikely to be going anywhere. It's be cool though.
Holy Raft protocol is the blockchain of cloud.
k3s doesn't require etcd, I'm pretty sure GKE uses Spanner and Azure uses Cosmos under the hood.
and it's pretty modular too, so it can even serve as the host for the bespoke whatever that's needed
though I remember reading the fly.io blog post about their custom scheduler/allocator which illustrates nicely how much of a difference a custom in-house solution makes if works well
Sorry, this is just BS. etcd is a fifth wheel in most k8s installations. Even the largest clusters are better off with something like a large-ish instance running a regular DB for the control plane state storage.
Yes, etcd theoretically protects against any kind of node failures and network partitions. But in practice, well, nobody really cares about the control plane being resilient against meteorite strikes and Cthulhu rising from the deeps.