Real-timeexperimental

Local-First Sync Engine

A sync engine for local-first applications. The client owns a SQLite database in the browser (via WASM), every write goes there first, and a small server reconciles edits across clients. I built this to understand whether the local-first promise (offline, instant, multiplayer, but still synced) is actually achievable for everyday CRUD apps in 2026. Short answer: yes, but conflict resolution is still where the design work lives.

SQLiteWASMIndexedDBWebSocket

What this is

A lab, not a product.

Features

Learnings

Technologies

Capabilities

What it does

The features that actually got built and run in this prototype.

feature_01.ts

Local SQLite database via WASM with persistent storage in IndexedDB

feature_02.ts

Automatic sync to the server with a write-ahead log, not a snapshot diff

feature_03.ts

Conflict resolution strategies per-table, configurable from last-write-wins to manual merge

feature_04.ts

Offline queue management with optimistic UI and clear rollback on server rejection

feature_05.ts

Selective sync patterns sharing the same primitives as the real-time collaboration blueprint

The stack

What it is built with

The libraries and runtimes I picked for this lab and why they earned their place.

SQLite

WASM

IndexedDB

WebSocket

What I learned

Learnings, in order of how much they surprised me

The things I would tell another engineer before they tried the same experiment.

SQLite WASM gives you excellent query performance. The browser is genuinely a database host in 2026

Conflict resolution strategies depend heavily on data type. Counters, sets, and text each want different rules

Sync granularity has a huge impact on bandwidth. Row-level diffs beat whole-document syncs by an order of magnitude

Local-first changes the product, not just the architecture. Users notice the instant feel immediately

Note: This is an experimental project in the experimental stage. It is a learning exercise and technical exploration rather than a production-ready solution. Patterns and code may change.

Real-time

Related labs

Other explorations in this area.

alpha

Real-time Collaborative Editor

An exploration of CRDTs and operational transforms for building Google Docs-style collaborative editing experiences. I wanted to understand the offline story end to end, not just the happy multiplayer path. This prototype runs on Y.js with a tiny WebSocket relay, persists everything to IndexedDB on the client, and reconciles edits when you come back online. The interesting work is in the seams: presence, undo, and how you tell a user that their last 12 minutes of typing just collided with someone else's.

Want me to build something like this for you?

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