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:
- CPU
- 1,000 × 20 s / 3,600 × $0.0385
- $0.21
- Memory
- 1,000 × 90 s / 3,600 × 4 × $0.021875
- $2.19
- CPU
- 1,000 × 60 s × 2 × $0.0000276944
- $3.32
- Memory
- 1,000 × 60 s × 4 × $0.0000036667
- $0.88
- CPU
- 1,000 × 20 s / 3,600 × $0.025
- $0.14
- Memory
- 1,000 × 60 s / 3,600 × 4 × $0.0075
- $0.50
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 and Runtime vs AWS Lambda MicroVMs.
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 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.
Facts on this page were checked on 26 October 2026.