Distributed systems, made tangible

CRDT Constellation

Three replicas can disappear offline, rewrite the same sentence, and return in any message order. No central winner. No fake merge animation. Every character is an immutable operation in a deterministic sequence CRDT.

Local-first lab 3 replicas · 0 servers seeded · inspectable · replayable

Simulated network

A route is usable only when both endpoint devices are online.

3 online
Network routes among Atlas, Beacon, and Cygnus A triangular network. Bright lines are connected routes; dim dashed lines are partitioned routes. A B C
Editing is always localTyping commits immediately to that device, even while isolated.
Delivery can be out of orderMissing anchors wait safely until their insert operation arrives.
Reconnect exchanges every missing opPlay drains all usable routes; the final state is schedule-independent.

No messages in flight.

Convergence invariant

Equal operation sets must produce equal visible text.

Converged
Replica state hash
00000000

All three replicas contain the same operations, resolve every anchor, and render the same document.

Boot-time algorithm check pending…

Three offline-capable editors

Isolate any device, type directly into its document, then reconnect. Remote operations never overwrite local state; they join it.

AtlasReplica A
Lamport
0
Operations
0
Hash
00000000
BeaconReplica B
Lamport
0
Operations
0
Hash
00000000
CygnusReplica C
Lamport
0
Operations
0
Hash
00000000

Each editor changes only its own replica. Use the Online button to isolate or reconnect that device.

Message queue

Select an operation to inspect its immutable ID, anchor, and ordering key.

0 queued 0 ready

    Why every replica agrees

    The sequence is a tree rooted at HEAD, rendered depth-first.

    same anchor → Lamport clock ↓ → device ID ↓ → local sequence ↓

    New text anchors to the visible character immediately before the cursor. Concurrent siblings use the total order above. Deletes leave tombstones, so later inserts never lose their anchor.

    Operation inspector

    Choose a queued row

    Reset installed the same base operations on all three replicas.

    Recently delivered