# Fly Machines vs AWS Lambda MicroVMs: Firecracker by the machine or the baseline

Runtime Cloud (withruntime.com) costs 58% less than a Fly Machine; both rivals run Firecracker, Lambda in AWS.

## Which is better, Fly Machines or AWS Lambda MicroVMs?

It depends on whether you run on AWS. For agent sandboxes that wait on a
model, Runtime is cheapest:
$0.64 for the job, against $1.53 on Fly Machines
and $4.20 on Lambda, and it keeps memory across pauses for
as long as you have credit. Pick Fly Machines for long-running apps in many regions next to
Fly's volumes and Postgres. Pick Lambda MicroVMs for sandboxes tied into AWS
identity and networking.

## At a glance

|           | Fly Machines                                                          | AWS Lambda MicroVMs                                                    | Runtime                                                            |
| --------- | --------------------------------------------------------------------- | ---------------------------------------------------------------------- | ------------------------------------------------------------------ |
| Isolation | Firecracker microVM                                                   | Firecracker microVM                                                    | Firecracker microVM, own kernel                                    |
| Price     | `performance-2x` with 4 GB, $0.0916704 an hour, `iad` | $0.2522 an hour for 2 vCPUs and 4 GB | $0.03125 an hour waiting, $0.08 busy, for 2 and 4 GiB |
| Largest   | 16 performance vCPUs and 128 GB                                       | Up to 4 vCPUs and 8 GB                                                 | 16 vCPUs and 64 GiB, paid                        |
| Idle      | Root disk is temporary; suspend only at 2 GB or less                  | Suspend keeps memory and disk, up to 8 hours                           | Pause keeps memory and processes while you have credit             |
| Regions   | 17                                                                    | AWS regions                                                            | One US region                                                      |

## Same hypervisor, about a third of the price

A performance vCPU on Fly is a whole core held for the Machine. Even so, the
shape costs about a third of Lambda's per hour. Lambda's premium buys AWS
integration and suspend with memory for up to eight hours; Fly Machines
suspend only at 2 GB of memory or less.

## Cost for the same job

2 vCPU, 4 GiB, 60 seconds a run, 20 CPU-seconds of work, 1,000 runs:

```
Machines  Size   1,000 × 60 s / 3,600 × $0.0916704                = $1.53

Lambda    CPU    1,000 × 60 s × 2 × $0.0000276944              = $3.32
          Memory 1,000 × 60 s × 4 × $0.0000036667              = $0.88
          Total                                                  $4.20

Runtime   CPU    1,000 × 20 s / 3,600 × $0.025                = $0.14
          Memory 1,000 × 60 s / 3,600 × 4 × $0.0075           = $0.50
          Total                                                  $0.64
```

Both rivals charge by size, so keeping both CPUs busy for the whole minute changes neither: $1.53 on Machines and $4.20 on Lambda, with $1.33 on Runtime.

## Which one to pick

- **Fly Machines** for long-running apps in many regions, alongside Fly's
  volumes and Postgres.
- **Lambda MicroVMs** for sandboxes tied into AWS identity and networking.
- **Runtime** for agent sandboxes at the lowest cost, with memory kept across
  pauses while you have credit.

See [Runtime vs Fly.io](/docs/fly-alternative) and
[Runtime vs AWS Lambda MicroVMs](/docs/aws-lambda-microvms-alternative).

## Runtime Cloud

Runtime costs 58% less than a Fly Machine and 85% less than a Lambda
MicroVM on the same job. One thousand one-minute runs of a 2 vCPU, 4 GiB sandbox,
each with 20 CPU-seconds of work, cost $1.53 on Fly Machines, $4.20 on AWS
Lambda MicroVMs and $0.64 on Runtime.

Runtime bills the CPU the code uses, so most of that gap is waiting time you
no longer pay for. Start on the free usage with `npx withruntime login`; code
that calls Fly's Machines API moves by the [migration guide](/docs/migrate).

## Sources

Fly.io prices checked 25 October 2026.

Fly Machines rates checked 25 October 2026; Lambda MicroVMs rates checked 25 October 2026.

- [Fly.io pricing](https://fly.io/pricing/)
- [AWS Lambda pricing](https://aws.amazon.com/lambda/pricing/), [Lambda MicroVMs](https://aws.amazon.com/lambda/lambda-microvms/)
- Runtime [pricing](/docs/pricing)

Facts on this page were checked on 26 October 2026.