Show HN: Syncular – offline-first SQL sync with TypeScript and Rust cores
github.com
github.com
I feel projects like this for local first and projects like Iroh for connectivity over NAT and through firewalls need to come together more.
It would be could to have a drop in framework for this.
Trying to guess what's going on from what is there... looks like conflicts are raised on a per row basis, and the app resolves the conflicts.
Per-row is going to make it hard to handle a lot of data models. Maybe there's some way to see the whole transaction, but how? And how can you see the server vs local data? You'll want that for many cases.
It's right to leave it to the app to resolve conflicts -- there is no one-size-fits-all answer to this. But by providing no tools and, seemingly pushing everything through a per-row API, it's going to be essentially impossible for apps to get things right. You'll end up with incoherent data -- data that isn't valid within one node, and nodes different from each other. Generally, not what you want when you implement sync.
(If it is manually written I don't trust the LLM-written docs.)
CRDTs are opt-in per column. A row can keep normal, queryable fields like project_id, status, and title, while one doc column stores Yjs/yrs bytes. Concurrent edits to that column are merged by the server; normal columns still use versions and explicit conflicts. Flutter uses yrs through the shared Rust core.
The trade-off is that SQL can’t query inside the CRDT document. Anything you need for filtering, joins, or aggregates should remain an ordinary column. That boundary gives you relational queries without giving up CRDTs where they’re really useful.
I’d be interested in your feedback on the Flutter client. I chose a very small C ABI—five hand-written dart:ffi bindings into the Rust core, rather than generating a large FFI surface. The app-specific schema, row types, subscriptions, and typed SQL/SYQL queries are generated from the shared schema IR using syncular generate. I’d love to hear how that feels compared with your flutter_rust_bridge setup.
More detail: https://syncular.dev/concepts-crdt/ https://syncular.dev/platform-flutter/
Hope one day offline first will be a default and a solved problem.
In my separate benchmark harness, Syncular currently does considerably better than the tested PowerSync setup. For example, 100k bootstrap is ~0.57s vs ~6.5s and offline replay ~35ms vs ~5.1s. Those are early results from one environment, though, not a universal claim (https://github.com/bkniffler/offline-sync-bench).
I've used PowerSync in the past with a huge initial bootstrap sync and was very frustrated by the performance back then (ca 1 year ago), which was one of the reasons to create my own library.
PowerSync is much more mature today obviously and still a great and proven tool.
Firstly, it's awesome that you are using @sqlite.org/sqlite-wasm for your client-side SQLite database. We really like wa-sqlite ourselves.
We're currently implementing this proposal https://github.com/orgs/powersync-ja/discussions/376, which will speedup the sync throughput a lot - this was a natural next step for us as we have users with massive datasets (syncing a million plus rows).
Sidebar: What has your experience with OPFS+SQLite been like on sqlite-wasm? We have seen our fair share of issues on Safari/web kit.
sqlite-wasm with opfs-sahpool has mostly behaved. No OPFS in private mode, storage may be evicted, handles can’t be passed to workers, and webviews may close them when backgrounded.
We open SQLite inside one dedicated worker and proxy other tabs through it, so that avoids some of the mess. Tauri uses native SQLite.
How do you handle browser storage eviction? I shipped a DuckDB-Wasm in-browser and found that survives reloads isn’t isnt really reliable.
Since pending writes live in the OPFS SQLite database, does the recommended setup request persistent storage or warn the user that an unsynced outbox could disappear if the origin is evicted?
Whats your app?
The issue I found most difficult architecturally was how to deal with staying responsive on first sign in with a large DB. I ended up with a system I called “materialisation on demand” where it will search the server and download only those rows ahead of time.
EDIT: I also ended up using multiple local databases to ensure responsive writes during heavy synching activity.
The app is https://www.benko.app/ it’s available on iOS, android, Mac and windows.
I’ll keep refining it (talking about docs, tests, benchmarks etc). LLMs are involved throughout Syncular, as they are in my other projects, but this sure wasn't prompted into existence, its been built on and off over a lot of time. Have spent years deep in the offline-first rabbit hole. Most code, design and its trade-offs come from that experience and predate LLMs.
In 2019 I built an offline-first datastore called debe. It used CRDTs and multi-master replication and never became something I could confidently ship. It did teach me that convergence is only a small part of sync. The difficult parts are durable writes, authorization changes, lost acknowledgements, schema upgrades, bounded bootstrap, and explaining what happened after something fails.
I eventually came back to the problem and built Syncular over the last year.
Every client has a real SQLite database: sqlite-wasm on OPFS in the browser and native SQLite elsewhere. Writes apply locally and enter a durable outbox in the same transaction. A server-authoritative commit log validates and orders them, using explicit scopes resolved inside the application backend.
The protocol is written down independently of the implementations. SSP2 is currently a draft, with canonical binary encoding and golden byte vectors. There are independent TypeScript and Rust client cores, both run against the same 95-scenario conformance catalog. The Rust core is exposed through Swift, Kotlin, Flutter, React Native, Tauri, Rust, and a small C API.
It also includes realtime WebSocket sync, resumable bootstrap segments, explicit conflict evidence, authorization revocation and local purge, windowed replicas, blobs, optional CRDT columns, per-column encryption, and typesafe generated queries for five languages. Important boundaries: it is pre-1.0, self-hosted, and there is no managed service or peer-to-peer mode. Native packaging maturity still varies by ecosystem.
Let me know what you think, I'm happy about feedback!
Demo: https://demo.syncular.dev Protocol: https://github.com/syncular/syncular/blob/main/docs/SPEC.md Background: https://syncular.dev/blog/offline-first-writes/ Docs: https://syncular.dev/