etcd KV, Watch, and Lease API

Astra implements the following etcd-compatible services:

• KV
• Watch
• Lease

For canonical RPC request/response fields, use the generated proto contract in crates/astra-proto/proto/rpc.proto.

RPC Surface

KV Service

RPC	Purpose
Range	Point read and prefix LIST reads.
Put	Key write with optional lease association.
DeleteRange	Point delete or range delete.
Txn	Compare-and-swap and conditional operations.
Compact	Logical compaction signal.

Watch Service

RPC	Purpose
Watch(stream WatchRequest)	Bidirectional stream for create/cancel/progress watch control and event delivery.

Lease Service

RPC	Purpose
LeaseGrant	Create lease ID/TTL binding.
LeaseRevoke	Revoke lease and detach keys.
LeaseKeepAlive(stream LeaseKeepAliveRequest)	Lease heartbeat stream.
LeaseTimeToLive	Inspect TTL state and keys.
LeaseLeases	List current leases.

Compatibility Notes

• Focus is control-plane compatibility for validated scenarios.
• Unsupported historical edge semantics should be validated case-by-case before migration.