SSE vs WebSocket for Sports Data

Reconnection & Reliability

SSE wins. The EventSource API handles reconnection automatically with exponential backoff. On reconnect, it sends aLast-Event-ID header so the server can replay missed events. With WebSocket, you must implement reconnection logic, track connection state, re-authenticate, and re-subscribe — plus handle the gap in data between disconnect and reconnect.

Infrastructure Compatibility

SSE wins. SSE is just HTTP, so it works through any proxy, load balancer, CDN, or firewall that supports regular web traffic. WebSocket requires an HTTP upgrade handshake that some corporate proxies, older load balancers, and strict firewalls block. Cloudflare, nginx, and AWS ALB all support WebSocket, but you may hit issues in enterprise environments.

Dynamic Subscriptions

WebSocket wins. If you need to change what data you're receiving mid-stream (e.g., switching from NBA to NFL, or adding a market type), WebSocket lets you send a new subscribe message without disconnecting. With SSE, you must close the connection and open a new one with updated query parameters. For most use cases this reconnection takes milliseconds and isn't a problem, but WebSocket is cleaner for highly dynamic UIs.

Latency

Tie. Once the connection is established, both protocols deliver data with effectively identical latency. SharpAPI measures sub-89ms P50 on both SSE and WebSocket endpoints. The real latency bottleneck is the upstream data pipeline — how quickly odds are collected from sportsbooks and processed — not the delivery protocol.

SSE with EventSource (JavaScript)

const eventSource = new EventSource(
  'https://api.sharpapi.io/api/v1/stream?sport=basketball_nba',
  { headers: { Authorization: 'Bearer YOUR_API_KEY' } }
)

eventSource.onmessage = (event) => {
  const odds = JSON.parse(event.data)
  console.log('Odds update:', odds.event, odds.bookmaker, odds.market)
}

eventSource.onerror = () => {
  // EventSource auto-reconnects by default
  console.log('Connection lost, reconnecting...')
}

WebSocket (JavaScript)

const ws = new WebSocket('wss://ws.sharpapi.io')

ws.onopen = () => {
  // Authenticate and subscribe
  ws.send(JSON.stringify({
    type: 'auth',
    apiKey: 'YOUR_API_KEY'
  }))
  ws.send(JSON.stringify({
    type: 'subscribe',
    sport: 'basketball_nba',
    markets: ['h2h', 'spreads']
  }))
}

ws.onmessage = (event) => {
  const data = JSON.parse(event.data)
  console.log('Update:', data)
}

// Can update subscriptions on the fly
ws.send(JSON.stringify({
  type: 'subscribe',
  sport: 'football_nfl'
}))