Fly Machines alternatives
The 6 alternatives below are grouped by kind of sandbox, and each says what it does differently from Fly Machines. Start from whatever made you look: missing GPUs, session limits, self-hosting, pricing or isolation.
Why teams look beyond Fly Machines
A fast, well-priced Firecracker VM primitive for teams that want to assemble their own sandbox layer; for an agent-ready product on the same infrastructure look at Fly.io Sprites.
- No sandbox SDK: no exec, file or snapshot-fork API for agents — you bring your own control plane inside the VM
- Only an official Go client; other languages must be generated from the OpenAPI spec
- Machine placement can fail when a region is out of capacity, per the docs
- GPU availability is unclear after Fly scaled back its GPU plans; pricing page lists no GPU rates
Fly Machines alternatives, by kind
Hosted sandbox platforms
SDK-driven sandboxes you create, run code in and destroy through an API.
E2B
Open-source cloud sandboxes for AI agents, each a Firecracker microVM, with pause/resume, snapshots and forking.
- Firecracker microVM
- Open source
- Self-hostable
- BYOC
- Pause/resume
How it differs: Code interpreters and short-to-medium-lived agent tasks that need microVM isolation, with an open-source self-host path. The safe default for most agent builders: mature, open source, microVM-isolated and widely supported.
Persistent VMs and agent computers
Full, long-lived virtual machines that an agent keeps, forks and returns to.
Fly.io Sprites
Persistent, hardware-isolated Linux computers for AI agents with a durable 100 GB disk, checkpoints, and no compute charges while idle.
- MicroVM
- Pause/resume
How it differs: Long-running, stateful agent computers that should cost nothing while idle. The most natural “persistent computer per agent” model, with idle-free billing.
Compute platforms with sandboxes
General serverless or app platforms that also offer sandboxes, often with GPUs.
Koyeb Sandboxes
Ephemeral microVM sandboxes on Koyeb’s serverless platform for AI-generated code, with CPU or GPU and scale-to-zero.
- MicroVM
- GPU
How it differs: Teams already on Koyeb or in the Mistral ecosystem that want GPU-capable ephemeral sandboxes. Promising GPU-capable microVMs, but still preview — evaluate as it matures within Mistral.
Railway Sandboxes
On-demand Linux VMs inside a Railway environment with forks, checkpoints, Docker, private networking to your services and per-second billing; generally available since September 2026.
- Linux VM
- Snapshots
How it differs: Coding agents and test runs that need to reach your Railway databases and services over the private network. The natural sandbox for teams already deploying on Railway, strongest when agents need private-network access to existing services.
Unikraft Cloud
Millisecond-start microVMs built from Dockerfiles on a modified Firecracker VMM, with stateful scale-to-zero, live forking ("branching") and checkpoints, plus a Sandbox SDK for agents.
- microVM (modified Firecracker)
- Self-hostable
- BYOC
- GPU
- Pause/resume
How it differs: Agent fleets that need thousands of sandboxes per server, millisecond stateful wake-ups and live forking of running environments. A density- and latency-focused microVM platform whose stateful forking and shielded egress suit large agent fleets, if you can work with unpublished pricing.
Cloud provider code execution
Managed code-execution tools from AWS, Azure, Google Cloud and OpenAI.
AWS Lambda MicroVMs
A Lambda resource type that runs a full Amazon Linux 2023 environment in a Firecracker microVM, restored from a pre-built snapshot, with suspend/resume and an HTTPS endpoint per VM.
- Firecracker microVM
- Pause/resume
How it differs: AWS-native agent sandboxes and interactive sessions that need VM isolation, an inbound endpoint and cheap idle time via suspend. The AWS-native way to get Firecracker-isolated, suspendable sandboxes with a per-VM endpoint, within an 8-hour lifetime and without a higher-level sandbox SDK.
Fly Machines vs alternatives
| Sandbox | Isolation | Open source | Self-host / BYOC | Cold start (vendor) | Max session | Snapshots / pause | GPU | SDKs |
|---|---|---|---|---|---|---|---|---|
| Fly Machines | Firecracker microVM | No | No / No | <1 s start (claimed) | Not documented | Yes / Yes | Not documented | Go, CLI, REST API |
| AWS Lambda MicroVMs | Firecracker microVM | No | No / No | sub-second to seconds (claimed) | 8 h | Yes / Yes | No | Python, JavaScript/TypeScript, PHP, CLI, REST API |
| E2B | Firecracker microVM | Yes | Yes / Yes | Not documented | 1 h / 24 h (Pro) | Yes / Yes | No | Python, JavaScript/TypeScript |
| Fly.io Sprites | MicroVM | No | No / No | 0.1–2 s wake | Unlimited | Yes / Yes | No | JavaScript/TypeScript, Go, Python, Elixir |
| Koyeb Sandboxes | MicroVM | No | No / Not documented | Not documented | Up to 24 h | Not documented / Not documented | Yes | Python, JavaScript/TypeScript |
| Railway Sandboxes | Linux VM | No | No / No | Not documented | No cap (idle 30 min default) | Yes / No | Not documented | JavaScript/TypeScript, CLI, GraphQL API |
| Unikraft Cloud | microVM (modified Firecracker) | No | Yes / Yes | <10 ms (claimed) | Not documented | Yes / Yes | Yes | JavaScript/TypeScript, Python, Go, CLI, REST API |
Frequently asked questions
What are the main alternatives to Fly Machines?
Is there an open-source alternative to Fly Machines?
Cite this page
Agent Sandboxes. (2026). Fly Machines alternatives. agentsandboxes.org. Last reviewed November 9, 2026. https://agentsandboxes.org/alternatives/fly-machines/
Found an error or a missing sandbox? Submit a correction — every entry links to the sources it relies on.