Current documented limits
| Constraint | Current value | Scope | Verified source |
|---|---|---|---|
| Machines API action rateRead operations and app deletion have separate documented rates. | Most actions: 1 request/second with burst 3 | Per API action scope | Fly.ioAug 22, 2026 |
| persistent volume sizeA volume can attach to only one Machine at a time. | 1 GB default; 500 GB maximum | Per volume | Fly.ioAug 22, 2026 |
| snapshot retentionSnapshots are a recovery feature and remain tied to volume behavior. | 5 days default; configurable 1–60 days | Fly Volumes | Fly.ioAug 22, 2026 |
| ephemeral root performanceThe root filesystem is ephemeral and has different durability from a Fly Volume. | Up to 2,000 IOPS and 8 MiB/s | Machine root filesystem | Fly.ioAug 22, 2026 |
How to apply Fly.io limits safely
The monitored baseline covers Machines API action rate, persistent volume size, snapshot retention, ephemeral root performance. Treat these as separate constraints rather than one platform-wide capacity number: a workload can fit one row and still fail another because the plan, model, endpoint, runtime, region, invocation mode, or account scope differs.
- Match the production workload to the exact scope printed beside each value and confirm it in the active Fly.io console, configuration, or response headers.
- Measure the serialized request, token volume, duration, concurrency, storage, or connection demand at realistic percentiles, then preserve headroom for bursts and retries.
- Check every adjacent layer—client, SDK, gateway, proxy, queue, database, and downstream service—for a smaller effective limit before changing architecture.
Specific limit pages
These pages exist because the constraint has a distinct implementation or troubleshooting intent. Closely related keyword variations stay consolidated.
Fly Machines API Rate Limits
Fly Machines API Rate Limits, verified against Fly.io's official documentation with scope, implementation impact, caveats, and a direct check.
Fly Volume Size Limits
Fly Volume Size Limits, verified against Fly.io's official documentation with scope, implementation impact, caveats, and a direct check.
Fly Volume Snapshot Retention
Fly Volume Snapshot Retention, verified against Fly.io's official documentation with scope, implementation impact, caveats, and a direct check.
Fly Machine Ephemeral Disk Limits
Fly Machine Ephemeral Disk Limits, verified against Fly.io's official documentation with scope, implementation impact, caveats, and a direct check.