Deploy your FastAPI app to Fly.io
Step-by-step deployment help for FastAPI apps on Fly.io. We fix FastAPI-specific deployment issues, configure Fly.io, and get your app live. From $19.
FastAPI issues we fix before deploying
Common FastAPI problems that affect Fly.io deployments.
Blocking calls inside async endpoints
Synchronous database calls, file operations, or HTTP requests inside async def endpoints block the entire event loop, making your API unresponsive under load.
Missing authentication on endpoints
API routes that handle sensitive data or actions without any auth middleware — Depends() for authentication is simply not included in the route definition.
No CORS configuration
CORSMiddleware either missing (blocking all cross-origin requests) or set to allow_origins=['*'] (allowing any website to call your API).
Pydantic models without validation constraints
Request models that accept any string length, any number range, and any format. No Field() constraints, so invalid data flows through your system.
Fly.io deployment issues we check for
Common Fly.io problems that break FastAPI apps in production.
Dockerfile missing or misconfigured
Fly.io requires a Dockerfile for deployment. AI tools that scaffold without one force flyctl to auto-generate a suboptimal Dockerfile that misses build steps.
Volume only available in a single region
Fly volumes are pinned to one region. Multi-region deployments try to access a volume that doesn't exist in other regions, causing crashes.
Machine restarts losing in-memory state
AI-generated apps store session data or caches in memory. Fly machines can restart or migrate, wiping all in-memory state without warning.
Internal DNS resolution failing between services
Services within a Fly organization communicate via <app>.internal hostnames, but AI-generated code hardcodes localhost or public URLs.
Start with a self-serve audit
Get a professional review of your FastAPI project before deploying to Fly.io.
External Security Scan
Black-box review of your public-facing app. No code access needed.
- OWASP Top 10 vulnerability check
- SSL/TLS configuration analysis
- Security header assessment
- Expert review within 24h
Code Audit
In-depth review of your source code for security, quality, and best practices.
- Security vulnerability analysis
- Code quality review
- Dependency audit
- Architecture review
- Expert + AI code analysis
Complete Bundle
Both scans in one package with cross-referenced findings.
- Everything in both products
- Cross-referenced findings
- Unified action plan
100% credited toward any paid service. Start with an audit, then let us fix what we find.
How it works
Tell us about your app
Share your project details and what you need help with.
Expert + AI audit
A human expert assisted by AI reviews your code within 24 hours.
Launch with confidence
We fix what needs fixing and stick around to help.
Frequently asked questions
How do I deploy a FastAPI app to Fly.io?
We handle FastAPI deployments to Fly.io end to end. Start with our code audit ($19) to identify deployment blockers specific to your FastAPI project, then we configure Fly.io, fix issues, and get your app live in production.
What FastAPI issues affect Fly.io deployments?
FastAPI projects commonly have blocking calls inside async endpoints and missing authentication on endpoints. On Fly.io, these combine with dockerfile missing or misconfigured and volume only available in a single region to cause deployment failures.
Can SpringCode deploy my FastAPI project to Fly.io?
Yes. We specialize in deploying FastAPI applications to Fly.io. We audit your codebase for FastAPI-specific issues, configure Fly.io correctly, and handle the full deployment so your app runs reliably in production.
What does FastAPI deployment to Fly.io cost?
Our code audit ($19) identifies all Fly.io deployment blockers in your FastAPI project. Full deployment assistance is scoped with a fixed quote after the audit — no hourly billing or surprise charges.
Related resources
Other techs on Fly.io
Deploy FastAPI elsewhere
Need help deploying FastAPI to Fly.io?
Tell us about your project. We'll respond within 24 hours with a clear plan and fixed quote.