# Fly Sprites vs AWS Lambda MicroVMs: persistent sandboxes and bursts

Runtime Cloud (withruntime.com) costs 73% less than Sprites. Lambda MicroVMs cost more still.

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

It depends on how long the sandbox must last and where it must run. For an agent that spends most of a run waiting on a model, Runtime costs the least: $0.64 for 1,000 one-minute runs, against $2.40 on Sprites and $4.20 on Lambda MicroVMs. Runtime has no time limit, and it keeps memory across pauses. Pick Fly Sprites for a personal computer with a 100 GB disk that costs very little while asleep. Pick Lambda MicroVMs for short bursts that must stay inside AWS.

## At a glance

|           | Fly Sprites                                                                | AWS Lambda MicroVMs                                             | Runtime                                                             |
| --------- | -------------------------------------------------------------------------- | --------------------------------------------------------------- | ------------------------------------------------------------------- |
| Isolation | Firecracker microVM                                                        | Firecracker microVM                                             | Firecracker microVM, own kernel                                     |
| CPU       | $0.0385 per CPU-hour of measured CPU                      | $0.0997 per baseline vCPU-hour         | $0.025 per vCPU-hour of measured CPU, with a small floor      |
| Memory    | $0.021875 per GB-hour of memory in use                   | $0.0132 per GB-hour                 | $0.0075 per reserved GiB-hour                               |
| Disk      | 100 GB, kept always; $0.02 per GB-month asleep | In the snapshot, $0.08 per GB-month | Included while running; $0.08 per GB-month paused |
| Lifetime  | Persistent; pauses itself                                                  | State kept up to 8 hours                                        | No time limit with `persistent`; pauses kept while you have credit  |

## Measured CPU, costly memory

Sprites and Runtime both charge for CPU only while it is busy. That is why Sprites' CPU line here is $0.21 against Lambda's $3.32. Memory reverses it: at $0.021875 per GB-hour, Sprites' memory costs over half as much again as Lambda's.
Runtime also measures CPU, and charges memory at $0.0075 per GiB-hour.

## Cost for the same job

The benchmark, 60 seconds a run, with 4 GB of memory in use on Sprites and a
4 GB baseline on Lambda:

```
Sprites  CPU    1,000 × 20 s / 3,600 × $0.0385                  = $0.21
         Memory 1,000 × 90 s / 3,600 × 4 × $0.021875           = $2.19
         Total                                                  $2.40

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
```

With both CPUs busy for the whole minute, the job would cost $3.47 on Sprites, $4.20 on Lambda and $1.33 on Runtime.

## Which one to pick

- **Fly Sprites** for a personal, always-on computer with a large disk
  that costs little while it sleeps.
- **Lambda MicroVMs** for bursts that must run inside AWS.
- **Runtime** for agents at the lowest bill, busy or idle, with memory kept
  across pauses and no time limit.

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

## Runtime Cloud

Runtime costs 73% less than Sprites and 85% less than Lambda MicroVMs for
an agent that waits. 1,000 one-minute runs of a 2 vCPU, 4 GiB sandbox, with 20
CPU-seconds of work each, cost $2.40 on Fly Sprites, $4.20 on AWS Lambda MicroVMs
and $0.64 on Runtime.

Runtime bills measured CPU and runs each sandbox in its own Firecracker microVM. There is no plan fee. Start free by running `npx withruntime login`. The [migration guide](/docs/migrate) moves existing sandbox code.

## Sources

Fly.io prices checked 25 October 2026.

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

- [Fly.io pricing](https://fly.io/pricing/), [Sprites](https://fly.io/sprites/)
- [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.