REFERENCE / FAQ QUICKFIRE
FAQ quickfire
One-line answers with a source for each. If the answer is not here, the sources below are where to look next. Anything the sources do not settle is marked [verify].
This page is drawn from https://fly.io/docs/about/pricing/, https://fly.io/docs/getting-started/essentials/, https://fly.io/docs/reference/architecture/, https://fly.io/docs/launch/autostop-autostart/, https://fly.io/docs/volumes/overview/, https://fly.io/docs/networking/private-networking/, https://fly.io/docs/sprites/, https://fly.io/docs/about/support/ and the Fly.io blog.
| Question | Answer | Source |
|---|---|---|
| What is a Fly App? | “A Fly App is an abstraction for a group of Fly Machines running your code on Fly.io.” | https://fly.io/docs/apps/overview/ |
| What is a Machine? | A Firecracker microVM that launches quickly in any supported region. | https://fly.io/docs/getting-started/essentials/ |
| What isolates customers? | Firecracker microVMs on dedicated physical servers. | https://fly.io/docs/reference/architecture/ |
| How many regions? | 17 rows in the regions table (derived by counting them). Run fly platform regions for the live list. | https://fly.io/docs/reference/regions/ |
| How fast does a stopped Machine start? | Usually “well under a second”. A new one can take “low double digit seconds” to create. | https://fly.io/docs/machines/overview/ |
What does fly launch do? | Detects your framework and writes fly.toml. Add --no-deploy to stop before the first deploy. | https://fly.io/docs/getting-started/essentials/, https://fly.io/docs/launch/volume-storage/ |
| How many Machines does a first deploy make? | Two for redundancy, if you define no process groups. | https://fly.io/docs/launch/deploy/ |
| Default deploy strategy? | rolling, one Machine at a time. canary, bluegreen and immediate also exist. | https://fly.io/docs/launch/deploy/ |
| How do I build the image? | Dockerfile (default), buildpacks, or a prebuilt image. | https://fly.io/docs/reference/builders/ |
| Is there a platform fee? | “Fly.io bills for the resources you use, with no monthly platform fee.” | https://fly.io/docs/about/pricing/ |
| Smallest always-on app? | $2.19 per 30 days, for shared-cpu-1x with 256MB. | https://fly.io/docs/about/pricing/ |
| Is there a free trial? | $1 of credit for 7 days, with no card. Trial Machines stop after 5 minutes. | https://fly.io/docs/about/free-trial/ |
| What does a stopped Machine cost? | Only its rootfs, $0.15/GB per month. | https://fly.io/docs/about/pricing/ |
| Do builders cost money? | Not currently: building and registry storage are free, with notice promised before any change. | https://fly.io/docs/about/pricing/ |
| Egress price? | $0.02/GB in North America and Europe, $0.04/GB in Asia Pacific, Oceania and South America, $0.12/GB in Africa and India. Inbound is free. | https://fly.io/docs/about/pricing/ |
| IP address costs? | Shared IPv4 and IPv6 are free. A dedicated IPv4 is $2/month. | https://fly.io/docs/about/pricing/ |
| Can I get a discount? | Reservation blocks give 40% off compute in a region, for example $36/year for $5/month of shared usage. | https://fly.io/docs/about/pricing/ |
| Does Fly Proxy scale to zero? | Yes: auto_stop_machines and auto_start_machines stop and start existing Machines. It never creates or destroys them. | https://fly.io/docs/launch/autostop-autostart/ |
| How slow is a cold start? | “about 2 seconds or more for common apps”. Suspend resumes in a few hundred milliseconds. | https://fly.io/docs/launch/autostop-autostart/ |
| Does Fly Proxy terminate TLS? | By default for most public apps, yes. | https://fly.io/docs/reference/fly-proxy/ |
| What is Anycast here? | IP blocks announced from every datacenter over BGP, so clients reach the nearest one. | https://fly.io/docs/networking/services/ |
| Can I route a request to another region? | Yes, with the fly-replay response header. | https://fly.io/docs/networking/dynamic-request-routing/ |
| Do my apps talk privately by default? | Yes, over the org’s 6PN, with .internal DNS. | https://fly.io/docs/networking/private-networking/ |
| How do I keep an app private and autostoppable? | Flycast: fly launch --flycast, then <app>.flycast. | https://fly.io/docs/networking/flycast/ |
| Does Flycast do HTTPS? | No. “Flycast is HTTP-only.” | https://fly.io/docs/networking/flycast/ |
| Can my laptop join the private network? | Yes, with fly wireguard create and a WireGuard app. | https://fly.io/docs/networking/private-networking/ |
| Are volumes shared between Machines? | No. One volume attaches to one Machine, and it belongs to one app. | https://fly.io/docs/volumes/overview/ |
| Are volumes network storage? | No. “It is not network storage.” | https://fly.io/docs/volumes/overview/ |
| Biggest volume? | 500GB, and you can extend it but not shrink it. | https://fly.io/docs/volumes/overview/ |
| Volume backups? | Daily snapshots, 5 days by default, 1 to 60 configurable. Do not treat them as the primary backup. | https://fly.io/docs/volumes/overview/ |
| Volume price? | $0.15/GB per month, provisioned, even when detached. | https://fly.io/docs/about/pricing/ |
| Where do secrets live? | An encrypted vault, injected as environment variables at boot. | https://fly.io/docs/apps/secrets/ |
| Can Fly host Postgres for me? | Managed Postgres, from $38/month (Basic) to $1,922/month (Performance), plus $0.28/GB storage. | https://fly.io/docs/about/pricing/ |
| Can I upgrade Postgres in place? | No. Create a new cluster and use pg_dump and pg_restore. | https://fly.io/docs/postgres/ |
| Is the old Fly Postgres supported? | It is listed as unsupported: you manage it yourself. | https://fly.io/docs/about/pricing/ |
| Is LiteFS supported? | No: the docs say LiteFS is outside Fly.io’s scope of support. | https://fly.io/docs/litefs/ |
| Object storage? | Tigris, S3-compatible, created with fly storage create. | https://fly.io/docs/tigris/ |
| Are there GPUs? | GPU Machines exist, but a “v2 of the product” should not be expected (Kurt Mackey, 2025-02-14). | https://fly.io/blog/wrong-about-gpu/ |
| Compliance? | SOC2 Type 2 audited and will sign BAAs. | https://fly.io/docs/about/healthcare/ |
| Is there an SLA? | The support page lists a “99.9% uptime SLA” under Enterprise ($2,500+/month). Credit tiers and exclusions are not public [verify] with sales. | https://fly.io/support |
| What support is there? | Community is free. Standard $29, Premium $199, Enterprise from $2,500 a month. | https://fly.io/docs/about/pricing/ |
| Where is the status page? | status.flyio.net. | https://fly.io/docs/about/support/ |
| Will Fly move my Machine? | Yes, to healthy hosts: it stops, forks any volume, and starts on the new host with a new 6PN address. | https://fly.io/docs/reference/machine-migration/, https://fly.io/docs/networking/private-networking/ |
| What is a Sprite? | “Sprites are persistent, hardware-isolated Linux environments for running arbitrary code.” | https://fly.io/docs/sprites/ |
| Sprite size? | 8 vCPUs, platform-managed memory, 100 GB storage. | https://fly.io/docs/sprites/concepts/lifecycle/ |
| How fast does a Sprite wake? | Warm 100 to 500ms, cold 1 to 2 seconds. | https://fly.io/docs/sprites/concepts/lifecycle/ |
| Do checkpoints save processes? | No: disk is saved, memory and running processes are not. | https://fly.io/docs/sprites/concepts/checkpoints/ |
| Is a Sprite URL public? | Authenticated by default. sprite config update --url-auth public opens it. | https://fly.io/docs/sprites/quickstart/ |
| Sprite price? | $0.0385/CPU-hour, $0.021875/GB-hour of memory, $0.000683/GB-hour of hot storage. | https://fly.io/sprites |