Does NestJS Work With Fly.io?
NestJS runs excellently on Fly.io with minimal configuration, providing a seamless experience for deploying scalable Node.js applications globally.
Quick Facts
How NestJS Works With Fly.io
NestJS deploys to Fly.io with straightforward containerization using Docker. Fly.io's platform handles the heavy lifting of running your NestJS application across multiple regions, providing automatic scaling, SSL termination, and zero-downtime deployments. The developer experience is smooth: you containerize your NestJS app, configure a fly.toml file, and deploy via the Fly CLI. NestJS's modular architecture pairs well with Fly.io's microservices-friendly infrastructure, allowing you to split monolithic apps into distributed services if needed. The main architectural consideration is handling environment-specific configuration—use NestJS's ConfigModule to manage different settings across environments, and leverage Fly.io's secrets management for sensitive data. Database connections and WebSocket support work seamlessly, though you should be mindful of connection pooling when scaling horizontally since Fly.io can spin up multiple instances of your app.
Best Use Cases
Quick Setup
npm install -g @nestjs/cli && npm install -g flyctl# Create NestJS app
nest new my-app && cd my-app
# Initialize Fly.io
fly launch
# Update Dockerfile (Fly.io auto-generates)
# Ensure port matches NestJS (default 3000)
# In main.ts, bind to 0.0.0.0
await app.listen(3000, '0.0.0.0');
# Set environment variables
fly secrets set NODE_ENV=production
# Deploy
fly deploy
# Check logs
fly logsKnown Issues & Gotchas
Database connection pooling exhaustion when scaling to multiple instances
Fix: Configure connection limits in your TypeORM/Prisma setup and use pgBouncer or similar for PostgreSQL to manage connection pooling at the database level.
Session affinity not guaranteed across regions, breaking session-based auth
Fix: Use JWT tokens or store sessions in Redis instead of in-memory storage. Deploy a Redis instance on Fly.io or use a managed service like Upstash.
Cold starts can exceed 10 seconds if Docker image is large or dependencies take time to load
Fix: Optimize Docker layers, use multi-stage builds, consider lazy-loading heavy modules, or upgrade to Fly.io's paid tier for reserved capacity.
File uploads don't persist across instances; temporary files are lost on restart
Fix: Use cloud storage (AWS S3, Google Cloud Storage) or Fly.io's persistent volumes for file persistence.
Alternatives
- •Express.js on Heroku—simpler framework but less structured, Heroku has higher costs
- •Fastify on AWS Lambda with API Gateway—serverless approach, better for sporadic traffic patterns
- •Django on Render—different language but similar global deployment experience with easier free tier
Resources
Related Compatibility Guides
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