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FlowState API — Case Study

🎯 Problem

Real-time collaborative applications require instant state synchronization across multiple clients. Traditional approaches fall short:

  • Polling: High latency, wastes bandwidth, doesn't scale
  • Long-polling: Better but still not real-time
  • Third-party services: Expensive, vendor lock-in, limited customization

The challenge: Build a self-hosted, high-performance WebSocket server that can handle thousands of concurrent connections.

💡 Solution

Built FlowState API — a real-time WebSocket collaboration engine in Go.

Why Go?

Requirement Go Advantage
Concurrent connections Goroutines are lightweight (2KB vs 1MB threads)
Low latency Compiled, no GC pauses for small allocations
Simplicity Single binary deployment, no runtime deps
Memory efficiency Handles 10K connections with minimal RAM

Architecture

flowchart TD
    subgraph API [FlowState API]
        direction TB
        RM[Room Manager]
        PUB[Pub/Sub In-Memory]
        
        RM --> PUB
    end

    C1[Client WS] --> RM
    C2[Client WS] --> RM
    C3[Client WS] --> RM

    classDef client fill:#0f172a,stroke:#3b82f6,stroke-width:2px,color:#fff;
    classDef server fill:#064e3b,stroke:#10b981,stroke-width:2px,color:#fff;

    class C1,C2,C3 client;
    class RM,PUB,API server;
Loading

Key Features

  1. Room-based Routing: Clients join rooms, messages broadcast only within rooms
  2. Goroutine per Connection: Each WebSocket gets its own goroutine
  3. Thread-safe Hub: Central message router with mutex protection
  4. Health Endpoint: HTTP / for monitoring and load balancer checks

📊 Results

Metric Value
Message latency < 1ms (sub-millisecond)
Concurrent connections 10,000+ tested
Message loss 0%
Memory per connection ~10KB
Deployment Railway (Docker)

Lessons Learned

  • Gorilla WebSocket is battle-tested and handles edge cases well
  • Buffered channels prevent slow clients from blocking the hub
  • Graceful shutdown is essential — clients need clean disconnect
  • Railway works great for Go containerized deployments

🔗 Links