Key Takeaway
By the end of this blueprint you will have an end-to-end streaming architecture that delivers LLM tokens to the client via Server-Sent Events, handles structured output parsing mid-stream, recovers gracefully from connection drops, and progressively renders markdown with code blocks on the client side.
Prerequisites
- A Next.js or FastAPI backend capable of streaming responses
- Familiarity with Server-Sent Events (SSE) or WebSocket protocols
- An LLM provider API that supports streaming (Anthropic, OpenAI)
- React or equivalent frontend framework for client-side rendering
SSE vs WebSocket for LLM Streaming
Server-Sent Events (SSE) is the right choice for most LLM streaming use cases. LLM generation is unidirectional — the server sends tokens to the client, and the client does not need to send data back during generation. SSE works over standard HTTP, passes through CDNs and load balancers without special configuration, supports automatic reconnection with event IDs, and is simpler to implement than WebSocket. Use WebSocket only when you need bidirectional communication during generation, such as mid-stream cancellation or real-time collaborative editing.
| Feature | SSE | WebSocket |
|---|---|---|
| Direction | Server to client only | Bidirectional |
| Protocol | HTTP/1.1 or HTTP/2 | Custom upgrade from HTTP |
| Load balancer support | Native | Requires sticky sessions or upgrade support |
| Auto-reconnection | Built-in with Last-Event-ID | Manual implementation |
| Complexity | Low | Medium-High |
| Best for | LLM token streaming | Interactive collaboration, gaming |
Server-Side Streaming Implementation
Unlock the full Knowledge Base
This article continues for 11 more sections. Upgrade to Pro for full access to all 93 articles.
That's just $0.11 per article
- Full access to all blueprints, frameworks, and playbooks
- Interactive checklists with progress tracking
- Downloadable templates (.xlsx, .pptx, .docx)
- Quarterly Technology Radar updates