If you’ve explored building real-time collaboration, you’ve probably come across Yjs. It’s one of the most popular CRDT frameworks for syncing shared state, but running it in production with a WebSocket server quickly exposes more complexity than it first appears. You need to manage connection states, handle offline clients, and scale sessions across servers.
The good news? You don't have to build all of this from scratch, and the technical decisions you make early on will either accelerate your product development or become a maintenance headache down the road. For teams looking to focus on their core product rather than collaboration infrastructure, a real-time collaboration SDK provides these same features through higher-level APIs without requiring deep technical implementation of WebSocket servers and CRDT synchronization.
TLDR:
Yjs WebSocket servers handle real-time collaboration but require complex scaling infrastructure
Production deployments need sticky sessions, pub/sub patterns, and 24/7 monitoring expertise
Memory usage grows with active documents; horizontal scaling breaks without message coordination
Teams often spend months on basic setup plus ongoing maintenance instead of core features
Velt provides 25+ collaboration features in as little as 10 lines of code vs building custom infrastructure
What is Yjs WebSocket Server
The Yjs WebSocket server implements a conventional client-server model where multiple clients connect to a single endpoint, and the server acts as the central hub for distributing document updates and awareness information among connected users. This architecture uses Yjs's conflict-free replicated data types (CRDTs) to make sure that concurrent edits from different users can be merged without conflicts.
At its core, the WebSocket provider creates persistent connections between clients and the server, allowing real-time synchronization of document state. When a user makes changes to a shared document, those changes are encoded as Yjs updates and transmitted through the WebSocket connection to the server, which then broadcasts them to all other connected clients working on the same document.
The server maintains document state in memory and can optionally persist it to storage backends. This approach works well for many collaborative applications, from text editors to design tools, because it provides low-latency updates while handling the complex conflict resolution that makes real-time collaboration possible.
However, building and maintaining this infrastructure involves substantial complexity. You need to handle connection management, implement proper error recovery, design scaling strategies, and maintain data consistency across server restarts.
The Yjs WebSocket server excels at handling the fundamental synchronization challenges of collaborative editing, but scaling it to production workloads requires major additional infrastructure work.
The y-websocket documentation provides detailed technical specifications, while the GitHub repository contains the reference implementation that many teams use as their starting point.
Core Features of Yjs WebSocket Architecture
The Yjs WebSocket server includes several core features that make it a strong foundation for collaborative applications. Cross-tab sync keeps documents consistent across multiple windows, awareness protocol enables presence data like live cursors and selections, and authentication integrates with existing user systems for access control. Persistence can also be added to support document recovery and offline use.
Feature | Description | Use Cases |
|---|---|---|
Cross-tab sync | Keeps multiple tabs synchronized | Multi-window workflows, session recovery |
Awareness protocol | Real-time presence and cursor data | Live cursors, user indicators, selections |
Authentication | Header and cookie-based auth | User permissions, access control |
Persistence | Optional document storage | Document recovery, offline support |
The architecture provides resilience with automatic reconnection and queuing during network interruptions, ensuring documents remain consistent. Together these features create a solid base for collaboration, but implementing them in production still requires expertise in WebSocket lifecycle management and CRDT synchronization.
The Yjs fundamentals guide provides deeper technical details, while the WebSocket API documentation covers the underlying browser technologies.
Scaling Challenges with Yjs WebSocket Servers
The scalability limitations of Yjs WebSocket servers become clear once you move beyond prototypes. Memory usage grows with active connections and documents, since each server maintains full state and awareness for every client. A single instance may handle hundreds of concurrent connections, but performance degrades as memory pressure increases.
Horizontal scaling is harder. Yjs documents must remain consistent across clients, so simply adding servers behind a load balancer does not work. Without coordination, clients on different servers miss updates. Solving this requires pub/sub or shared state layers such as Redis, which add infrastructure dependencies and potential failure points.
Connection affinity also matters. Clients need to stay connected to the same server or you must implement complex state migration for failover and rebalancing. This sticky session requirement limits flexibility and complicates deployment.
Finally, persistence adds another layer of complexity. Teams must decide when to persist state, how to handle concurrent writes across servers, and how to recover from failures. The simple in-memory model used in single-server setups becomes inadequate for high availability.
Scaling Yjs WebSocket servers is harder than it looks
Even with Redis or Kafka, you still need sticky sessions, state coordination, and persistence strategies. Many teams spend months on this infrastructure instead of product development.
The Yjs community discussions reveal common scaling pain points, while WebSocket scaling best practices provide general architectural patterns that apply to Yjs deployments. These scaling challenges explain why many teams eventually migrate to managed solutions.
Production Deployment Considerations
Running Yjs WebSocket servers in production requires ongoing monitoring, fault tolerance, resource management, and security. Teams need visibility into metrics such as connection health, memory usage, and synchronization performance to prevent failures.
Resilience means planning for crashes, network partitions, and client disconnects through retry logic, state recovery, and failover mechanisms. Scaling also introduces challenges like memory leaks, stale sessions, and abandoned documents that must be cleaned up automatically.
Security involves more than authentication. Rate limiting, input validation, and defenses against malicious clients are critical. Together, these factors create a continuous operational burden that many teams underestimate.
Reliable operation at scale also requires 24/7 monitoring and incident response processes, which few teams account for until problems appear in production.
Alternative Collaboration Solutions with Velt
While Yjs provides excellent CRDT foundations, building production-ready collaboration features requires a lot of additional work. Velt offers a complete alternative that builds upon the same CRDT principles while providing a complete collaboration layer out of the box.
Pre-built Components vs Custom Implementation
Instead of manually implementing user presence with Y.Map instances and custom UI components, Velt provides ready-to-use comments and presence indicators. You get Figma-style contextual commenting, real-time cursors, and user awareness with just a few lines of code.
Managed Infrastructure
Yjs requires you to manage WebSocket servers, handle reconnection logic, and implement offline synchronization. Velt provides enterprise-grade infrastructure with 99.999% uptime, automatic scaling, and reliable networking that handles edge cases you might not even know exist.
Advanced Features Beyond CRDTs
While Yjs handles data synchronization, collaborative apps need much more. Velt includes recording features, voice and video huddles, notification systems, and analytics tracking. These features would take months to build and maintain with a custom Yjs implementation.
Customization Without Complexity
Velt's customization options let you style components to match your brand while maintaining the underlying collaboration infrastructure. You get the flexibility of custom implementation without the maintenance burden.
Migration and Integration
Teams already using other collaboration solutions can easily migrate from Liveblocks or similar services. The migration process typically takes days rather than months of rebuilding collaboration features.
Even teams that attempt Redis- or Kafka-backed scaling often spend months maintaining infrastructure, only to end up with brittle systems that distract from core product work.
The value proposition is clear: get all the benefits of CRDT-based collaboration without the implementation complexity, ongoing maintenance, or feature gaps that come with building everything from scratch.
FAQ
How does a Yjs WebSocket server handle real-time synchronization?
The server maintains an in-memory representation of each document and uses Yjs CRDT updates to broadcast incremental changes to all connected clients. Each update is encoded, sent to the server, and merged across clients, ensuring eventual consistency without requiring explicit locking.
What makes horizontal scaling challenging for Yjs WebSocket servers?
State is maintained per document in memory, so running multiple instances requires cross-node coordination. Without a pub/sub or shared state layer, clients connected to different servers will miss updates. Typical solutions involve Redis or Kafka for broadcasting, combined with sticky sessions to keep clients attached to the same node, which increases infrastructure complexity.
What operational considerations exist when running in production?
Operators need to monitor metrics such as connection count, message throughput, memory per document, and reconnection rates. Fault tolerance requires strategies for handling node crashes, network partitions, and concurrent writes across distributed servers. Additional concerns include garbage collection of inactive documents, session cleanup, and mitigation of memory leaks.
How should persistence be implemented for collaborative documents?
By default, y-websocket stores state in memory only. For production, you typically integrate with a persistent backend (Postgres, Redis, S3, etc.) to handle recovery after restarts and to support offline clients. The challenge lies in ensuring atomic writes and consistency when multiple servers or processes update the same document state.
Why do some teams choose managed solutions instead of self-hosting?
Self-hosting requires building coordination layers, implementing retry and recovery logic, and hardening against malicious clients. Managed solutions abstract these layers by providing automatic scaling, state durability, and additional features like presence, comments, or analytics. This allows teams to focus engineering time on product features rather than distributed systems problems.
Final thoughts on building real-time collaboration infrastructure
Building and scaling Yjs WebSocket servers requires major infrastructure expertise that most teams underestimate. The complexity grows exponentially when you need production-ready features like load balancing, fault tolerance, and cross-server synchronization. Rather than spending months on collaboration infrastructure, an easy-to-use collaboration SDK can get you live collaboration features in minutes. Your engineering time is better spent on core product features that set your business apart.
