Realtime Sync Engine

A conflict-free replicated data type (CRDT) sync engine for building collaborative applications. Used in production by 3 companies.

Why I built it

I needed a sync engine for a side project. The existing options were either too heavy (Yjs), too opinionated (Automerge), or too commercial (Liveblocks). I wanted something small, fast, and dependency-free.

Features

• Three CRDT types — counter, register, sequence
• Rust core with TypeScript bindings via napi-rs
• WebSocket transport with offline support and replay
• 10k+ concurrent edits per document in benchmark
• Sub-50ms p99 sync latency on a 3-region deployment
• Zero dependencies in the runtime

What I learned

CRDTs are easy to understand and hard to implement. The math is clean; the engineering is messy. The hardest part was not the algorithm — it was designing the API so that developers did not need to understand CRDTs to use it.