Server-Sent Events Disconnecting in Cursor Application
Your Cursor-generated application uses Server-Sent Events (SSE) for real-time updates (live notifications, streaming responses, dashboards), but the SSE connection drops after a few seconds or minutes. Users see the real-time feed freeze, and the browser's EventSource silently reconnects only to disconnect again in a loop.
SSE connections are long-lived HTTP connections that must stay open indefinitely. This conflicts with many infrastructure components that expect short request-response cycles. Reverse proxies, load balancers, serverless platforms, and CDNs all have default timeouts that terminate SSE connections prematurely.
The issue is often intermittent — it works fine during development where there's no proxy layer, but fails in production where Nginx, Cloudflare, or a serverless platform sits between the client and server.
Error Messages You Might See
Common Causes
- Reverse proxy timeout — Nginx, Apache, or Cloudflare terminates idle connections after 60-120 seconds by default
- Serverless function timeout — Vercel (30s), Netlify (26s), and Lambda (15min max) kill long-running functions, terminating the SSE stream
- No keep-alive heartbeat — Without periodic data sent on the connection, intermediaries assume it's dead and close it
- Missing SSE headers — The response lacks required headers like
Content-Type: text/event-stream,Cache-Control: no-cache, orConnection: keep-alive - Response buffering enabled — Nginx or Node.js response compression buffers SSE data instead of streaming it, causing events to arrive in batches or not at all
How to Fix It
- Send heartbeat comments every 15-30 seconds — Send SSE comment lines (
: heartbeat\n\n) at regular intervals to keep the connection alive through proxies and load balancers - Configure proxy timeouts — For Nginx: set
proxy_read_timeout 86400s;andproxy_buffering off;. For Cloudflare: enable WebSockets/SSE in the dashboard or use Cloudflare Tunnel - Disable response buffering — Add
X-Accel-Buffering: noheader for Nginx, and disable compression on SSE endpoints - Implement robust client reconnection — Use EventSource's built-in reconnection with a custom
retry:field, and includeLast-Event-IDhandling to resume from where the client left off - Avoid serverless for SSE — If your SSE needs long-lived connections, deploy on a traditional server (VPS, container) rather than serverless functions. Alternatively, use a managed service like Ably or Pusher
- Set correct response headers — Ensure every SSE endpoint sends:
Content-Type: text/event-stream,Cache-Control: no-cache,Connection: keep-alive
Real developers can help you.
Anthony Akpan
Developer with 8 years of experience building softwares fro startups
legrab
I'll fill this later
Luca Liberati
I work on monoliths and microservices, backends and frontends, manage K8s clusters and love to design apps architecture
Rudra Bhikadiya
I build and fix web apps across Next.js, Node.js, and DBs.
Comfortable jumping into messy code, broken APIs, and mysterious bugs.
If your project works in theory but not in reality, I help close that gap.
Prakash Prajapati
I’m a Senior Python Developer specializing in building secure, scalable, and highly available systems. I work primarily with Python, Django, FastAPI, Docker, PostgreSQL, and modern AI tooling such as PydanticAI, focusing on clean architecture, strong design principles, and reliable DevOps practices. I enjoy solving complex engineering problems and designing systems that are maintainable, resilient, and built to scale.
Franck Plazanet
I am a Strategic Engineering Leader with over 8 years of experience building high-availability enterprise systems and scaling high-performing technical teams. My focus is on bridging the gap between complex technology and business growth.
Core Expertise:
🚀 Leadership: Managing and coaching teams of 15+ engineers, fostering a culture of accountability and continuous improvement.
🏗️ Architecture: Enterprise Core Systems, Multi-system Integration (ERP/API/ETL), and Core Database Structure.
☁️ Cloud & Scale: AWS Expert; architected systems handling 10B+ monthly requests and managing 100k+ SKUs.
📈 Business Impact: Aligning tech strategy with P&L goals to drive $70k+ in monthly recurring revenue.
I thrive on "out-of-the-box" thinking to solve complex technical bottlenecks and am always looking for ways to use automation to improve business productivity.
rayush33
JavaScript (React.js, React Native, Node.js) Developer with demonstrated industry experience of 4+ years, actively looking for opportunities to hone my skills as well as help small-scale business owners with solutions to technical problems
Matthew Butler
Systems Development Engineer @ Amazon Web Services
Taufan
I’m a product-focused engineer and tech leader who builds scalable systems and turns ideas into production-ready platforms.
Over the past years, I’ve worked across startups and fast-moving teams, leading backend architecture, improving system reliability, and shipping products used by thousands of users. My strength is not just writing code — but connecting product vision, technical execution, and business impact.
Jen Jacobsen
I’m a Full-Stack Developer with over 10 years of experience building modern web and mobile applications. I enjoy working across the full product lifecycle — turning ideas into real, well-built products that are intuitive for users and scalable for businesses.
I particularly enjoy building mobile apps, modern web platforms, and solving complex technical problems in a way that keeps systems clean, reliable, and easy to maintain.
You don't need to be technical. Just describe what's wrong and a verified developer will handle the rest.
Get HelpFrequently Asked Questions
Can I use SSE with serverless platforms like Vercel?
Standard SSE with long-lived connections doesn't work well with serverless platforms due to function execution time limits. Vercel supports streaming responses for up to 30 seconds. For longer connections, use a dedicated WebSocket service (Ably, Pusher, Supabase Realtime) or deploy the SSE endpoint on a traditional server.
How is SSE different from WebSockets?
SSE is unidirectional (server to client only), uses standard HTTP, and has built-in reconnection. WebSockets are bidirectional, use a separate protocol (ws://), and require manual reconnection logic. Use SSE when you only need server-to-client updates; use WebSockets when you need two-way communication.