Which is better, Blaxel or Prime Sandboxes?
It depends on whether your fleet mostly idles or mostly trains. For agents that wait on a model, Runtime has the lowest running cost: $0.64 on the benchmark, against $3.45 on Blaxel and $1.52 on Prime. Its paused storage is cheap, and a paused sandbox keeps its memory. Pick Blaxel for mostly idle fleets that resume in milliseconds. Pick Prime Sandboxes for dense RL training runs. An account starts with 1,024 sandboxes.
At a glance
| Blaxel | Prime Sandboxes | Runtime | |
|---|---|---|---|
| Isolation | Lightweight virtual machines | Hardware-virtualized microVM, own guest kernel | Firecracker microVM, own kernel |
| Billing | $0.0000115 per GB-second active, CPU included | $0.02 per vCPU-hour, $0.0125 per GiB-hour | $0.025 per measured vCPU-hour, $0.0075 per GiB-hour |
| Fleet | Over 100,000 at the same time on the top tier | 1,024 per account to start | 100 paid |
| Idle | Standby when connections close; ~25 ms resume | Idle timeout off by default, up to 24 hours | Pause or idle pause; memory kept while you have credit |
| Free start | Up to $200 of credit | None published | 100 free hours of a 1 GB machine in the first 30 days, no card |
Standby against low rates
Blaxel makes idle sandboxes nearly free. It moves them to standby about 15 seconds after
their connections close. Prime makes running sandboxes cheap per hour, but
it keeps billing until the sandbox ends or its optional idle timeout fires.
Runtime's idle pause, set with idlePauseSeconds, stops compute billing too.
It keeps memory for when the next request wakes the sandbox.
Cost for the same job
The benchmark runs 60 seconds a run, with 4 GB of active memory on Blaxel and a 5 GiB disk on Prime:
- Memory
- 1,000 × 75 s × 4 × $0.0000115
- $3.45
- CPU
- 1,000 × 60 s / 3,600 × 2 × $0.02
- $0.67
- Memory
- 1,000 × 60 s / 3,600 × 4 × $0.0125
- $0.83
- Disk
- 1,000 × 60 s / 3,600 × 5 × $0.0002
- $0.02
- 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 totals are $3.45 on Blaxel, $1.52 on Prime and $1.33 on Runtime.
Which one to pick
- Blaxel for fleets of mostly idle sandboxes that resume in milliseconds.
- Prime Sandboxes for dense RL training runs.
- Runtime for the lowest cost while sandboxes run, and cheap paused storage.
See Runtime vs Blaxel and Runtime vs Prime Sandboxes.
Runtime Cloud
Runtime costs 81% less than Blaxel and 58% less than Prime for the same job: 1,000 one-minute runs of a 2 vCPU, 4 GiB sandbox, each with 20 CPU-seconds of work. Blaxel prices memory alone. Prime prices every resource while it runs. Runtime prices the CPU the code used.
You can start free with npx withruntime login. To bring a Blaxel or Prime project across, read the migration guide.
Sources
Blaxel rates checked 25 October 2026; Prime Sandboxes rates checked 25 October 2026.
Facts on this page were checked on 26 October 2026.