Is there any alternatives to long polling for watching KV updates?
I’ve see consul uses protobuf https://github.com/hashicorp/consul/blob/main/proto/pbsubscribe/subscribe.proto . Is anything of that kind is available for public usage?
Also mb there exist any additions to consul that provides pub/sub service for watching KV updates in N-subs <–> 1-connection fashion?
Aside from long polling, Consul does not currently support any other mechanisms for watching KV changes. The gRPC / protobuf code you linked to was added in Consul 1.9, and is currently only used for a handful of internal RPC endpoints. Eventually we would like to migrate all internal RPC calls to this new gRPC transport (see https://github.com/hashicorp/consul/issues/6366).
Even longer term, we are also considering supporting gRPC for public API endpoints.