Core concepts
Languages & limits
What you can run, how big it can be, and how usage is metered.
Supported languages
| Language | Identifier | Runtime |
|---|---|---|
| Python | python | CPython 3.12 |
| Node | node | Node.js 22 LTS |
More languages are added based on demand. Need one that isn't listed? Tell us — it helps us prioritise.
Sandbox resources
Every sandbox — one-shot or session — runs with a fixed footprint:
| Resource | Value |
|---|---|
| vCPU | 1 |
| Memory | 512 MiB |
| Isolation | gVisor (hardware-virtualised syscall sandbox) |
| Network egress | Filtered through a proxy |
Plan limits
| Free | Pro | Enterprise | |
|---|---|---|---|
| Concurrent sandboxes | 3 | 25 | 100+ |
| Max run/exec timeout | 5 min | 60 min | Custom |
| Concurrent sessions | 1 | 10 | 50+ |
| Max session lifetime | 15 min | 60 min | Custom |
| Included credit | $10 one-time | Metered | Custom |
See pricing for the current plans. Exceeding your credit on the free tier returns 402 Payment Required.
Rate limits
The API is rate-limited to 60 requests per minute per API key. Exceeding it
returns 429 Too Many Requests; back off and retry. This limits request volume — it
is separate from the concurrency limits above, which cap how many sandboxes run at once.
Request size
code— up to 100,000 characters.- File
content(sessions) — up to 1,000,000 characters. - File
path— up to 1,024 characters.
How usage is metered
Usage is billed per vCPU-second and GiB-second of sandbox runtime, reported to Stripe as you go:
| Resource | Rate |
|---|---|
| CPU | $0.00001 per vCPU-second |
| Memory | $0.000003 per GiB-second |
One-shot runs are metered for their execution time; sessions are metered for their full lifetime (from ready to stopped), so kill sessions promptly.