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Show HN: SyncKit – Offline-first sync engine (Rust/WASM and TypeScript)

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Re: Show HN: SyncKit – Offline-first sync engine (Rust/WASM and TypeScript)

#3

Post by danbitengo »

Hey HN, I built SyncKit after shipping two local-first projects (RestBolt and Graft) and realizing there's no simple way to add cross-device sync.

The problem: Existing solutions are either too complex (Automerge/Yjs require learning CRDTs) or too restrictive (Firebase isn't truly local-first, Supabase has no offline support - issue #357 has been open 4+ years with 350+ upvotes).

SyncKit is the middle ground: simple API, works offline-first, self-hostable.

Technical highlights: - TLA+ formal verification: 118,711 states checked, caught bugs before implementation - Rust → WASM core (48.9KB gzipped) - 700+ tests including 80 chaos tests (zero data loss) - Server: Bun/Hono WebSocket (SDK works in any JS runtime) - Production-ready: v0.1.0 on npm and Docker Hub

Known limitations (v0.1.0): - LWW only - advanced CRDTs (Text, Counter, Set) coming in v0.2.0 - React hooks only - Vue/Svelte adapters planned - Reference server is Bun (Node/Deno coming v0.3.0)

Happy to answer questions about the CRDT implementation, TLA+ modeling, or WebSocket architecture.

GitHub: https://github.com/Dancode-188/synckit npm: @synckit-js/sdk

Re: Show HN: SyncKit – Offline-first sync engine (Rust/WASM and TypeScript)

#5

Post by danbitengo »

android521 wrote: post #4

Is support for react native on the roadmap?

Not yet, but it's definitely something I'm considering.

Right now v0.1.0 is React (web) only. I'm planning Vue/Svelte for v0.2.0, and React Native could absolutely be v0.3.0 or sooner if there's demand.

The nice thing is the core sync engine is Rust → WASM, so it's framework-agnostic. The main work is just creating the React Native bindings and not rebuilding the sync logic.

Are you working on something with React Native? Curious what your offline sync needs are because it'd help me prioritize what to build next.

Re: Show HN: SyncKit – Offline-first sync engine (Rust/WASM and TypeScript)

#7

Post by threatofrain »

danbitengo wrote: post #3

Hey HN, I built SyncKit after shipping two local-first projects (RestBolt and Graft) and realizing there's no simple way to add cross-device sync. The problem: Existing solutions are either too complex (Automerge/Yjs require learning CRDTs) or too restrictive (Firebase isn't truly local-first, Supabase has no offline support - issue #357 has been open 4+ years with 350+ upvotes). SyncKit is the middle ground: simple…

TLA+ checked! Whoa!

Re: Show HN: SyncKit – Offline-first sync engine (Rust/WASM and TypeScript)

#10

Post by danbitengo »

gagik_co wrote: post #8

This is impressive! After Realm depreciation I have been trying many different offline sync options, they are especially few on Dart… Dart-Rust binding generator is pretty great though so it’s nice this is in Rust. Will keep an eye on this.

Thanks! Yeah, Realm's shift in direction left a gap in the offline-first space.

I didn't build Dart bindings yet (Rust → WASM → TypeScript for v0.1.0), but since the core is in Rust, Dart bindings via dart_rust_bridge are definitely feasible. Would actually be a great addition.

Are you actively looking for a Realm replacement for a Dart project? Curious what your offline sync requirements are. It might help me prioritize Dart support

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