Crate kevy_scope 

kevy-scope — scoped multi-writer ownership table.

Phase 3 of the v3-cluster RFC: a key prefix (app:billing:) is declared to belong to one writer node; writes landing on any other node answer -MISDIRECTED writer is <host:port>. This crate is the pure-data “stone” layer — config-driven ownership table, longest-prefix routing, MOVE-SCOPE quiesce-window state machine — without any I/O. The kevy server’s cement layer plugs it in.

See .claude/rfcs/2026-06-18-v3-cluster.md ## Q3 resolution for the locked design (MOVE-SCOPE = option (a) quiesce-window; no write-shadowing, no 2PC, no per-key MIGRATE/ASK).

Anti-scope (don’t add):

• Cross-scope transactions (a single MULTI/EXEC may not touch keys in two scopes; the client splits by scope).
• Automatic scope migration on kevy-elect ANNOUNCE — operator- issued only.
• Write-shadowing during migration; the writer quiesces, ships, and only then flips ownership.

Quick start (config side)

use kevy_scope::{OwnershipTable, Scope};

let table = OwnershipTable::new(vec![
    Scope::new(b"app:billing:".to_vec(), "embed-billing-1".to_string())
        .with_fallback("server-eu-1".to_string()),
    Scope::new(b"app:auth:".to_vec(), "embed-auth-1".to_string()),
])
.expect("non-overlapping prefixes");

// Local node looks up routing for a key.
let routing = table.route(b"app:billing:invoice:42", "embed-billing-1");
assert!(routing.is_local_writer());

// Same key arriving on the wrong node:
let routing = table.route(b"app:billing:invoice:42", "server-eu-1");
// server-eu-1 is the fallback, not the live writer — depending on
// F4 fallback state, routing is Misdirected or Owned. See the
// `route_with_fallback_state` API for the state-aware lookup.
assert!(matches!(routing, kevy_scope::Routing::Misdirected { .. }));

Structs

MigrationState

One in-flight migration. Carries enough metadata so the server cement can encode -QUIESCED <prefix> migrating to <host:port> without re-resolving the target.

MigrationTable

Per-scope migration tracker. Insert order doesn’t matter; lookups are O(prefix-set-size), expected ≤ tens of entries even in the largest cluster.

OwnershipTable

Immutable ownership table. Build once at startup from [[cluster.scope]] config; share across reactor threads via Arc<OwnershipTable>.

Scope

One scope declaration: a key-prefix slice owned by writer, with an optional fallback server that takes over writes when the writer is flagged DOWN by kevy-elect.

Enums

MigrationError

Why MigrationTable::start refused.

OwnershipError

Reasons OwnershipTable::new can refuse a list of scopes.

Routing

Result of an crate::OwnershipTable::route lookup. Borrows the writer/target ids out of the table — caller copies only when it needs to log or encode them.