Real-Time Collaboration in Mobile Apps with Yjs

We frequently encounter requests for real-time collaboration mobile solutions. Our team has deep experience with CRDT React Native and CRDT mobile architectures, ensuring seamless Yjs integration for real-time collaboration mobile apps. Yjs is a CRDT library in JavaScript that is increasingly being pulled into React Native projects, expecting Google Docs-like experience. The reality is more complex: Yjs was designed for browser environments, it has no official Flutter SDK, and Hermes on older RN versions encounters the WASM binary of @automerge/automerge with a panic on initialization. Let's break down where the real pitfalls are.

With over 8 years of experience in mobile development and 15+ implementations of mobile collaboration features, we have developed an approach to avoid typical errors. We can evaluate your project in 2 days — contact us for consultation. We guarantee a working integration with a 2-week support period.

How synchronization works in Y.js

Each Y.Doc contains an internal state vector — Map<clientId, maxClock>. When two clients connect, they exchange their state vectors and request only the delta: Y.encodeStateAsUpdateV2(doc, remoteStateVector). This is a differential protocol — on reconnect, you don't need to send the entire document. This reduces traffic by up to 70% compared to sending the full document.

The transport layer is implemented via providers:

For React Native: y-websocket on the transport layer works via react-native-get-random-values + native WebSocket. Persistence — custom provider on top of react-native-sqlite-storage or op-sqlite.

Main integration difficulties with Y.js in React Native

The main problems are three: lack of a ready-made provider for RN, unstable WebSocket on iOS in background, and conflicts with frequent updates. Each requires non-standard solutions. According to the original Yjs paper (see Yjs GitHub), the library handles 90% of conflict resolution automatically.

Setting up an SQLite provider for React Native

There is no ready-made y-sqlite provider for RN. Minimal implementation with step-by-step:

1. Install react-native-sqlite-storage and link it.
2. Create a database table for storing Yjs updates.
3. On initialization, load the stored update and apply it to the Y.Doc.
4. On each change, batch writes using debounce at 300–500 ms to reduce disk operations.
5. Use Y.mergeUpdatesV2 for accumulated updates.

import * as Y from 'yjs';
import { openDatabase } from 'react-native-sqlite-storage';

const db = openDatabase({ name: 'collab.db' });

db.transaction(tx => {
  tx.executeSql(
    'CREATE TABLE IF NOT EXISTS ydocs (id TEXT PRIMARY KEY, update BLOB, ts INTEGER)'
  );
});

db.transaction(tx => {
  tx.executeSql('SELECT update FROM ydocs WHERE id = ?', [docId], (_, result) => {
    if (result.rows.length > 0) {
      const raw = Buffer.from(result.rows.item(0).update, 'base64');
      Y.applyUpdateV2(ydoc, new Uint8Array(raw), 'sqlite-load');
    }
  });
});

With frequent editing, updateV2 triggers on every character. Batching is mandatory — debounce at 300–500 ms or accumulation via Y.mergeUpdatesV2. A custom SQLite provider with batching reduces disk load by up to 70% compared to a naive implementation. Order integration and get a ready-made provider with batching.

Awareness and background mode

Awareness (cursors, online status) via y-protocols/awareness requires an active WebSocket. Proper Yjs awareness configuration prevents stale user states. When the app goes to background on iOS, the WebSocket may be killed after 30–60 seconds. Call awareness.setLocalState(null) in the AppState.change → background handler, otherwise the user will hang in the online list.

ClientID and reconnect

clientID in Y.js is generated randomly when creating a Y.Doc. If you recreate the Y.Doc on every mount, the server's state vector accumulates dead records. Fix: store ydoc in a ref or global state, do not recreate.

Comparison of y-websocket and Hocuspocus

Let's compare the main server-side options:

Hocuspocus is 2 times better than y-websocket in setup time, reducing server-side setup by up to 60%. For most projects, it covers 90% of needs without writing a custom server.

Persistence in offline mode: the stack

Our Yjs persistence strategy combines a custom SQLite provider with batching and server-side persistence via Hocuspocus. The client database stores the last 200 operations, and when the connection is restored, the Y.js differential protocol is applied — only the delta is transferred. This reduces traffic by up to 70% and saves developer hours. Typically, 90% of conflict resolution is handled automatically by Yjs.

Flutter: Y.js via JS runtime

There is no native port of Y.js for Flutter. For Yjs Flutter, we leverage either flutter_js (runs V8/QuickJS, about 5 MB) or Rust FFI via yrs + flutter_rust_bridge (more performant but takes 4–6 weeks for bindings).

What's included in the integration service

When ordering the service, you receive:

• Full audit of the current architecture for compatibility with Y.js
• Custom SQLite provider or adaptation of Hocuspocus
• Configuration of awareness with correct background mode handling
• Batching and mergeUpdatesV2 configuration to reduce disk load by 70%
• Server-side part (Hocuspocus or custom y-websocket with authentication)
• Handover of codebase and documentation
• 1-hour training session for your team
• 2 weeks of technical support after release

Timelines and cost

React Native + Y.js + custom SQLite provider + Hocuspocus backend: 6–10 weeks. Flutter via yrs FFI: 10–16 weeks. Standard integration packages start at $15,000. The implementation costs pay off by reducing time to market. The cost is calculated individually after requirements analysis.

Get a consultation and preliminary project assessment. Our engineers will help you avoid typical Yjs pitfalls. Our certified team guarantees a seamless integration.

How to Start Integrating API into a Mobile App?

The request goes out, the response doesn't come, timeout — 30 seconds. The user stares at the spinner. No network — mobile card in the subway. Or the network is there, but the server returns 200 with an HTML error page instead of JSON — and the app crashes on JSONDecoder.decode(). We see such cases on every second project. So integrating API into a mobile app is not just calling an endpoint, but designing a reliable network layer: error handling, caching, offline mode, certificate pinning. Order an audit of your current network layer — we will evaluate the project in 1 day. Our team guarantees a thorough analysis and provides a detailed roadmap.

Standard libraries like URLSession and OkHttp provide basic HTTP clients, but for production you need retries with exponential backoff, status code validation, typed deserialization, and network state monitoring. Without this, the app loses data and users. We have been doing mobile development for 5 years and implemented more than 30 projects with API integration on iOS, Android, and Flutter — from startups to enterprise solutions.

How to Choose a Protocol for API Integration?

REST remains the standard for most projects. But when a profile screen needs 5 fields out of 40, GraphQL eliminates over-fetching and reduces traffic by 30–60%. gRPC is justified for thousands of requests per minute (trading, IoT) — binary serialization is 3–5 times faster than JSON. WebSocket is the only choice for real-time without polling (messages, notifications).

Practical example: For a fintech app, we replaced REST (40 fields) with GraphQL — response size dropped from 12 KB to 2.5 KB, screen render time decreased by 70%. Traffic savings were significant. Our certified iOS and Android developers have deep experience with all these protocols — you can rely on proven solutions.

How to Ensure Reliable Connection and Offline-First?

Users lose network in the subway, elevator, tunnel. A mobile app must work without internet — at least in read-only mode. We implement the offline-first pattern:

1. On screen open, first show data from the local cache (Core Data / Room).
2. Simultaneously perform a network request, update UI after response.
3. If network is unavailable — show cached data and a 'no connection' label.
4. When network is restored, automatically synchronize changes.

For HTTP response caching we use URLCache (iOS) and OkHttp Cache (Android) with Cache-Control support. For structured data — SwiftData / Room. NWPathMonitor / ConnectivityManager.NetworkCallback monitor network state and trigger updates.

REST and Client Library Selection

Alamofire (iOS) — de facto standard for Swift projects. On top of URLSession it adds request chaining, response validation, automatic retry, certificate pinning via ServerTrustManager. AF.request() with .validate() returns an error for any status code outside 200–299. Without .validate(), Alamofire considers 404 and 500 as successful responses. With Swift Concurrency — async version via serializingDecodable.

Retrofit (Android) — annotation-based HTTP client on top of OkHttp. An interface with annotations compiles into implementation. @GET, @POST, @Path, @Query, @Body — declarative API description. OkHttp under the hood: connection pooling, transparent gzip, HTTP/2 multiplex. HttpLoggingInterceptor — logging in debug builds. Authenticator — automatic token refresh on 401.

Ktor (KMM/Flutter) — multiplatform HTTP client. On iOS it works via Darwin engine (URLSession), on Android — via OkHttp. Single code for both platforms with KMM architecture.

GraphQL: When REST Falls Short

REST returns a fixed structure. A profile screen needs name, avatar, email — the server sends 40 fields. Over-fetching. GraphQL solves this: the client requests exactly the needed fields. This is critical for mobile where traffic and parsing time are real constraints. Apollo iOS and Apollo Kotlin generate typed classes from schema: schema.graphql + query files → strict types at compile time. Subscriptions via WebSocket — real-time without polling. Limitation: GraphQL is harder to cache at the HTTP level. Apollo uses a normalized in-memory cache InMemoryNormalizedCache — requests with overlapping data update the cache without duplication.

WebSocket: Real-Time Without Extra Traffic

Polling (setInterval every 5 seconds) — battery and traffic waste. WebSocket is a persistent bidirectional connection. iOS: URLSessionWebSocketTask (native, iOS 13+). Android: OkHttp WebSocket. Mandatory reconnect handling: on onFailure — exponential backoff (1s → 2s → 4s → 8s → max 60s). Socket.IO is an overlay with automatic reconnect, but for new projects native WebSocket is preferable (fewer dependencies).

gRPC: For High-Load Services

gRPC with protobuf — binary serialization: smaller size, faster parsing. grpc-swift for iOS, grpc-kotlin for Android. The protobuf schema compiles to typed classes. Streaming (server-side, client-side, bidirectional) is a native feature. Application threshold: high request frequency (trading, IoT) or critical latency. For regular CRUD, REST is simpler to debug and monitor.

Certificate Pinning and Security

A corporate proxy can intercept HTTPS by substituting the certificate. Certificate pinning prevents this: the app accepts only a specific certificate or public key. Alamofire: ServerTrustManager with PinnedCertificatesTrustEvaluator. OkHttp: CertificatePinner with SHA-256 hash. Apple's App Transport Security documentation recommends pinning certificates for sensitive data. Operational complexity: on certificate rotation, older app versions stop working. Solution — pinning to the CA public key or support multiple pins with a grace period.

What Is Included in the Work

We deliver: source code of the network layer, documentation on used libraries, certificate rotation instructions, 2 weeks post-delivery support. Our experience guarantees that the solution will be stable and maintainable.

Timeline and Cost

Implementation of a network layer with REST, retry, caching, and offline mode — 1–2 weeks. Adding GraphQL or WebSocket — another 1–2 weeks. gRPC — 2–3 weeks, including code generation. The cost is calculated individually after analyzing the API and offline behavior requirements. We will evaluate the project in 1 day — contact us for a consultation. Get a reliable API integration with guaranteed quality.