How concurrent writes to a space reconcile. On one node, writes commit in order and the last committed write is a key's current value, with If-Match for optimistic concurrency; last-writer-wins across replicas over the hash-linked event DAG is the planned multi-host rule.

Conflict Resolution

Conflict resolution is how two concurrent writes to the same space reconcile. The intended multi-host rule is last-writer-wins (LWW) over the hash-linked event DAG (see epochs-dag), so replicas that have seen the same events pick the same winner without coordination. Today a space is served by one node, where writes are simply committed in order.

Role

It is the CRDT layer of consistency: combined with epoch ordering it would give eventual convergence across replicas — the precondition for multi-host replication.

Mechanics

On one node (shipped). Every write is committed in a transaction and stamped with its (seq, epoch, epoch_seq) position. A key's current value is the current_kv row written by the last committed write or delete (a delete leaves a tombstone), so concurrent writers to one key resolve in commit order. A client that must not overwrite someone else's change sends If-Match with the strong "blake3-…" ETag it last read; the write is refused if the key has changed since (see kv).

Across replicas (planned). No replication code is in production Node 1.17.3 or on main; a P2P prototype with its own reconciliation code exists only on an unmerged branch that the current plan does not port. LWW over the DAG's epoch ordering remains the design rule for when multi-host replication lands. Local read replicas (in progress) do not need conflict resolution: the host node stays the only writer.

Relationships

Resolves concurrent writes ordered by epochs-dag; a precondition for multi-host replication; underpins the eventual-consistency half of hybrid-consistency / consistency-model; single-node behavior is the kv current_kv state and If-Match.

Status & drift

Planned for cross-replica LWW. Single-node ordering and If-Match conditional writes are shipped in Node 1.17.3. See replication-and-discovery.

Sources

tinycloud-node @05c6a93 (Node 1.17.3): tinycloud-core/src/db.rs (transact, current_kv upkeep), tinycloud-core/src/models/current_kv.rs, tinycloud-node-server/src/routes/mod.rs:685 (strong If-Match ETags)
tinycloud-node branch feat/replication-e2e-bootstrap (unmerged): tinycloud-core/src/replication/{commit,recon}.rs (prototype)