Fly.io

Hardware-isolated VMs and sandboxes for apps and AI agents

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Screenshot of Fly.io, Hardware-isolated VMs and sandboxes for apps and AI agents

What is Fly.io?

Fly.io is a developer tool. Fly.io runs hardware-isolated Fly Machines that boot in under a second and bill by the second, plus Sprite sandboxes for untrusted or AI-generated code. Agents can drive deployment through MCP servers and official plugins. Managed Postgres, Redis, Tigris storage and Volumes cover data.

Fly.io is a compute platform built around Fly Machines: hardware-virtualized containers that boot in under a second and bill only for the time they actually run. Teams use it to run web applications, managed datastores and AI agents on the same primitive, spread across 18 or more regions, with a typical deploy time quoted at 500ms and a 99.9% uptime SLA. The pitch is consistency: the same API and the same building blocks serve a weekend prototype and a production fleet, so scaling up does not force a rearchitecture or a platform migration. The piece most relevant to agent work is Sprite. Each Sprite is a self-contained, hardware-isolated sandbox for running untrusted or AI-generated code, ready in under a second. You can checkpoint an entire environment, run anything inside it, and restore the checkpoint if something breaks. Billing follows actual CPU and memory consumption down to the second, which matters when agents spin environments up and down unpredictably. Storage pairs fast local NVMe with globally durable object storage, so state persists alongside the sandboxes. Agents can operate the platform without a human relaying commands. Fly.io ships CLIs and MCP servers designed to be agent-driven, including a Sprites MCP server for any agent that speaks MCP and official plugins for Claude Code, Codex, Cursor and OpenCode. An agent can deploy, scale and debug on its own. Data services include managed Postgres with backups, failover and connection pooling, Upstash-powered Redis for caching and queues, Tigris S3-compatible object storage, and Volumes for running your own datastore on a Machine. This is developer infrastructure, not a no-code product. The fit is engineering teams shipping containerized apps, and teams building agent tooling that needs real isolation and per-second economics. Compared with generic cloud VMs, Fly.io trades breadth of services for fast boot, simple regional placement and agent-native tooling. Framework guides cover Phoenix, SvelteKit, Rails, Docker, Django, Laravel, Next.js, Go and Rust.

How do you use Fly.io?

  1. 1Create a free account
    Sign up on the Fly.io site to get access to the dashboard and the CLI, which is the primary way to create Machines and deploy apps.
  2. 2Pick a framework or Docker guide
    Framework-specific guides for Phoenix, Rails, Django, Laravel, Next.js, SvelteKit, Go, Rust and plain Docker walk through packaging an existing app for Fly Machines.
  3. 3Choose a datastore
    Add managed Postgres with backups, failover and connection pooling, or attach Redis, Tigris object storage or a Volume for a self-managed database.
  4. 4Spin up a Sprite sandbox
    Create a hardware-isolated Sprite for untrusted or AI-generated code, then checkpoint the environment and restore it if a run breaks something.
  5. 5Wire an agent into the platform
    Install the Sprites MCP server or an official plugin for Claude Code, Codex, Cursor or OpenCode so an agent can deploy, scale and debug on its own.
  6. 6Plan support and scaling
    Review the support options and response times before going to production, since the platform advertises 18+ regions and a 99.9% uptime SLA.

Pros and cons

Pros

  • Machines boot in under a second and bill per second of actual CPU and memory use, which suits bursty agent workloadsAI
  • Sprite sandboxes are hardware-isolated and can be checkpointed and restored, giving AI-generated code a safe place to runAI
  • MCP servers and official plugins for Claude Code, Codex, Cursor and OpenCode let agents deploy and debug without human relayAI
  • Managed Postgres, Redis, Tigris object storage and Volumes keep data services on the same platform as computeAI
  • Start with free sign-up and the same primitives and API hold at production scale, with a 99.9% uptime SLAAI

Cons

  • No pricing figures appear on the homepage, so budgeting requires checking the pricing page or dashboard directlyAI
  • It is infrastructure for engineers: there is no visual builder, and container and networking concepts are assumedAI
  • Support tiers and guaranteed response times are tied to plans that the homepage does not spell outAI
  • The service catalogue is narrower than large hyperscalers, so some adjacent cloud products must be sourced elsewhereAI
  • Agent tooling depends on MCP and specific editors, leaving other workflows to the CLI and APIAI

How much does Fly.io cost?

Free trial

The homepage invites users to start for free through a sign-up page, and Sprite sandboxes are billed only for actual CPU and memory consumption down to the second. No trial length or credit amount is stated on the homepage.

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Support

The support team is described as engineers who write code, with guaranteed response times, single sign-on, SOC2 Type 2 attestation and CI/CD integration listed. Response times and channels depend on the plan chosen.

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Integrations

MCP servers, including the Sprites MCP server, plus official plugins for Claude Code, Codex, Cursor and OpenCode let agents drive deployment and debugging. Data integrations cover Upstash Redis and Tigris S3-compatible storage.

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Features

Fly Machines are hardware-virtualized containers with sub-second boot and per-second billing. Sprite sandboxes isolate untrusted or AI-generated code and support full environment checkpoint and restore. Storage spans local NVMe, Tigris S3-compatible object storage and Volumes. Managed Postgres, Upstash Redis and 18+ regions with a 99.9% uptime SLA support production scale.

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Frequently asked questions about Fly.io

  • Does Fly.io offer a free trial?
    The homepage invites users to start for free through a sign-up page, and Sprite sandboxes are billed only for actual CPU and memory consumption down to the second. No trial length or credit amount is stated on the homepage.
  • Does Fly.io have an API?
    Yes, Fly.io offers an API.
  • How do you use Fly.io?
    The walkthrough on this page covers 6 steps: 1. Create a free account 2. Pick a framework or Docker guide 3. Choose a datastore 4. Spin up a Sprite sandbox 5. Wire an agent into the platform 6. Plan support and scaling.
  • What platforms does Fly.io support?
    Fly.io is available on Web App, Linux, MacOS and Windows.
  • What does Fly.io integrate with?
    MCP servers, including the Sprites MCP server, plus official plugins for Claude Code, Codex, Cursor and OpenCode let agents drive deployment and debugging. Data integrations cover Upstash Redis and Tigris S3-compatible storage.
  • What are the limitations of Fly.io?
    No pricing figures appear on the homepage, so budgeting requires checking the pricing page or dashboard directly. It is infrastructure for engineers: there is no visual builder, and container and networking concepts are assumed. Support tiers and guaranteed response times are tied to plans that the homepage does not spell out.

Status

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Added10/21/2026

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