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Alex Spinov
Alex Spinov

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Fly.io Has a Free API: Deploy Docker Containers Globally in 35 Regions With a Generous Free Tier and Built-In Postgres

#webdev #docker #devops #api

Heroku killed its free tier. AWS is complex. Vercel is great for Next.js but not for a Go backend with WebSockets. Fly.io deploys any Docker container to 35 regions worldwide with a free tier that includes 3 shared VMs, 3GB persistent storage, and 160GB outbound bandwidth.

What Fly.io Actually Does

Fly.io is a platform that runs your Docker containers on bare-metal servers across 35 global regions. Unlike Heroku (which runs in one region), Fly.io places your app close to your users. Unlike AWS (which requires VPC/subnet/security group configuration), Fly.io needs one command.

The architecture: you push a Docker image (or Fly.io builds it from a Dockerfile), specify which regions you want, and Fly.io handles networking, TLS, load balancing, and health checks. Your app gets an Anycast IP — users are automatically routed to the nearest instance.

Fly.io also provides managed Postgres (free tier: 1 shared VM, 1GB storage), Redis, and S3-compatible object storage.

Quick Start 

# Install flyctl
curl -L https://fly.io/install.sh | sh
fly auth login

# Launch from any directory with a Dockerfile
fly launch
# Fly detects your framework, generates fly.toml

# Deploy
fly deploy
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Or deploy a specific Docker image:

fly launch --image nginx:alpine --name my-app
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Manage via API:

# List your apps
curl -H "Authorization: Bearer $(fly auth token)" \
  https://api.machines.dev/v1/apps

# Scale to multiple regions
fly scale count 3 --region iad,lhr,nrt

# Check status
fly status
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3 Practical Use Cases

1. Global API with Multi-Region Postgres 

# Create Postgres cluster
fly postgres create --name my-db --region iad
fly postgres attach my-db --app my-api

# Add read replicas in other regions
fly machines create --app my-db \
  --region lhr --size shared-cpu-1x
fly machines create --app my-db \
  --region nrt --size shared-cpu-1x
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Your API reads from the nearest Postgres replica. Writes go to the primary.

2. WebSocket Server 

# fly.toml
[http_service]
  internal_port = 8080
  force_https = true
  auto_stop_machines = false  # Keep alive for WebSockets
  auto_start_machines = true

[services.concurrency]
  type = "connections"
  hard_limit = 10000
  soft_limit = 8000
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Fly.io supports persistent connections natively — no WebSocket proxy configuration needed.

3. Background Workers 

# Create a separate process group for workers
fly scale count web=2 worker=3
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# fly.toml
[processes]
  web = "node server.js"
  worker = "node worker.js"
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Web servers handle HTTP. Workers process background jobs. Same deployment, different scaling.

Why This Matters

Fly.io fills the gap between Heroku (simple but US-only, no free tier) and AWS (global but complex). For indie developers and small teams who need globally-distributed infrastructure without the DevOps overhead, Fly.io is the pragmatic choice. The free tier is genuinely useful — not a 5-minute demo that times out.

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