What is Fly.io?
Fly.io is an application platform built around Fly Machines, which its documentation describes as fast-launching VMs that can be started and stopped at subsecond speeds. Users control the Machine count and each Machine's lifecycle, resources and region placement through a REST API or flyctl commands. Fly Launch offers an app-level path for teams that prefer app-wide configuration and containerized deployment over low-level Machine control. The docs also cover Sprites, Managed Postgres, networking and flyctl. The company was founded in 2017 and is based in Chicago.
Fly.io bills for the resources used, with no monthly platform fee and billing by the second while Machines run. The smallest always-on app costs $2.19 per 30 days. Volumes cost $0.15 per GB per month and are charged on provisioned capacity, and Managed Postgres runs from $38 per month for the Basic tier. Optional support plans start at $29 per month, and community support is free. Because volumes are tied to Machines, a stateful design needs its own replication and backup plan.
Key capabilities
- Machines Fast-launching VMs with controllable lifecycle, resources and region.
- Machines API and flyctl A REST API and command line for running and updating Machines.
- Fly Launch App-wide configuration and containerized deployment.
- Volumes Persistent storage billed per provisioned GB.
- Managed Postgres Database plans from Basic to Performance.
Where Fly.io fits
- Fly Machines and regions Machines are hardware-virtualized containers that launch instantly and run only when needed, in regions worldwide.
- Fly Launch deployment Deploy from GitHub or the CLI with fly launch, and Fly generates a Dockerfile for most popular frameworks.
- REST API and flyctl CLIs and MCP servers are built so agents can deploy, scale and debug on their own.
- Volumes Volumes hold your own database or persistent storage for Machines.
- Managed Postgres Postgres comes with backups, failover and connection pooling.
- Sprites sandboxes Hardware-isolated sandboxes run untrusted or AI-generated code.
- Object storage Tigris offers globally distributed, S3-compatible object storage.
- Isolation and attestation Machines are KVM hardware-isolated, and Fly states it is SOC2 Type 2 attested.
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