Control metadata. Distribute the data path.

The leader group owns cluster metadata. Workers own partition traffic. Ordinary reads and writes do not pass through the control-plane consensus group.

That separation lets Orbita add read replicas without expanding one global Raft group. Manual split and merge machinery exists; automatic size-triggered splitting remains roadmap work.

Leader group

The Raft-backed leader group owns the partition map, registered workers, keyspaces, placement, epochs, and failover decisions. It decides where work belongs without serving the normal key-value data path.

Workers

Each partition has one write owner and two full replicas. Workers keep an in-memory key index, serve partition reads, replicate writes, and route client requests.

Adding workers creates places to serve replicas and can increase read capacity when the read-replica target is configured accordingly. Holder placement and automatic redistribution onto new capacity are still being completed.

Replicated write path

A write is appended to the owner and replicas. Orbita acknowledges after two of the three WAL copies are durable.

client -> owner -> replica 1
                -> replica 2

acknowledge after 2 of 3 durable WAL appends

Partition epochs prevent an old owner from committing after ownership moves.

Object-backed storage

Workers flush immutable segments to S3-compatible object storage. One atomic manifest identifies the current durable state of a partition.

Object storage stays off the acknowledgement path. It makes durable data independent from any individual worker and lets replacement workers hydrate without copying the full database from a busy peer.

Partition movement

Range partitions create horizontal capacity. The manual split path can divide A—Z into A—M and N—Z without copying immutable parent segments. Automatic size-triggered splitting remains planned.

Deterministic simulation

The same runtime seams run under virtual time, network faults, disk faults, restarts, and seeded schedules. A failing seed becomes a replayable trace and a permanent regression test.