Quick answer
Fly.io documents ephemeral root performance as Up to 2,000 IOPS and 8 MiB/s. The root filesystem is ephemeral and has different durability from a Fly Volume.
Verified Aug 22, 2026Official source
Current limits
| Constraint | Current value | Scope | Verified source |
|---|---|---|---|
| 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 |
Why does this limit matter?
Write-heavy workloads can hit performance or durability limits even when capacity seems sufficient.
This value is scoped to Machine root filesystem; a different plan, runtime, model, endpoint, region, or account can produce a different effective constraint.
What should you check?
- Separate root-disk scratch writes from data that must survive Machine replacement.
- Confirm the exact plan, model, runtime, endpoint, region, and account that serve the failing workload.
- Record the observed value, response headers or configuration, timestamp, and source without logging secrets.
Important caveats
- Persistent volume performance depends on volume configuration and region.
- Treat the official source and live account configuration as authoritative if they differ from this verified snapshot.
HyperObserve reports the documented platform constraint. Your application, SDK, gateway, provider, region, or account can impose a lower effective limit.
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