Fly.io Cost Tuning

Overview

Fly.io charges per-second for running machines plus storage. Key levers: auto-stop idle machines, suspend instead of stop, right-size VMs, and clean up unused volumes.

Pricing Quick Reference

Resource	Free Tier	Cost
shared-cpu-1x (256mb)	3 VMs free	~$1.94/month each
shared-cpu-1x (512mb)	included	~$3.88/month
shared-cpu-2x (1gb)	-	~$11.62/month
Volumes	3GB free	$0.15/GB/month
Bandwidth	100GB free	$0.02/GB after
IPv4	1 free per org	$2/month each

Instructions

Strategy 1: Auto-Stop Idle Machines

# fly.toml — stop machines when no traffic
[http_service]
  auto_stop_machines = "stop"     # Full stop (cheapest, ~5s cold start)
  auto_start_machines = true
  min_machines_running = 0        # Allow all machines to stop
  # Use min_machines_running = 1 only for production apps

Strategy 2: Suspend for Faster Resume

# Suspend keeps memory state — resumes in ~100ms but costs ~$0.50/month
[http_service]
  auto_stop_machines = "suspend"

Strategy 3: Audit and Clean Up

# List all apps and their machine counts
fly apps list

# Find idle/stopped machines
fly machine list -a my-app --json | jq '.[] | select(.state != "started") | {id, state, region}'

# Destroy unused apps
fly apps destroy old-app --yes

# List and delete orphaned volumes
fly volumes list -a my-app
fly volumes destroy vol_xxx

Strategy 4: Right-Size VMs

# Check memory usage to see if oversized
fly ssh console -a my-app -C "cat /proc/meminfo | head -3"

# Downgrade if using <50% of allocated memory
fly scale vm shared-cpu-1x --memory 256 -a my-app

Cost Monitoring

# Check current month's usage
fly billing  # Shows org-level billing

# Estimate per-app cost
fly scale show -a my-app  # See VM count and size

Resources

Next Steps

For architecture design, see flyio-reference-architecture.