An interactive study companion for Martin Kleppmann's classic on reliable, scalable, and maintainable systems.
Multiple leaders accept writes in different datacenters — but conflict resolution becomes necessary.
Single-leader replication means cross-datacenter writes traverse WAN latency. Multi-leader allows each site to write locally, then replicate. The cost is write conflicts when two leaders modify the same data concurrently.
CouchDB replicates bidirectionally between edge nodes and cloud — ideal for offline-first mobile apps. Cassandra's multi-datacenter replication lets each region write locally. Figma-style collaborative editors use CRDTs so concurrent edits merge without a single leader bottleneck.
Collaborative design editing lets multiple users write concurrently from different regions. CRDTs and operational transforms merge conflicting layer edits without funneling every keystroke through one global leader.
// Canva-style real-time collaboration over WebSocket
const wss = new WebSocketServer({ port: 8080 });
wss.on("connection", (ws, req) => {
const designId = new URL(req.url!, "http://x").searchParams.get("designId");
ws.on("message", (raw) => {
const op = JSON.parse(raw.toString()) as DesignOperation;
// Apply CRDT / OT merge, then broadcast to all peers on this design
const merged = collabEngine.apply(designId!, op);
broadcast(designId!, { type: "sync", state: merged });
});
});