Which is better, Modal or Prime Sandboxes?
It depends on whether training and environments share one platform. For rollouts that mostly wait on a model, Runtime has the lowest bill: $0.64 for 1,000 one-minute runs, against $1.52 on Prime and $3.97 on Modal. It also forks a warmed-up environment with its memory and processes. Pick Modal when environments and GPU training should live together. Pick Prime Sandboxes for a thousand microVMs running at the same time inside Prime Intellect, though its GPU sandboxes are still listed as coming soon.
At a glance
| Modal Sandboxes | Prime Sandboxes | Runtime | |
|---|---|---|---|
| Isolation | gVisor, a user-space kernel | Hardware-virtualized microVM, own guest kernel | Firecracker microVM, own kernel |
| CPU | $0.1419 per physical core-hour (2 vCPUs), request or use | $0.02 per vCPU-hour while running | $0.025 per vCPU-hour of measured CPU, with a small floor |
| Memory | $0.0240 per GiB-hour, request or use | $0.0125 per GiB-hour | $0.0075 per reserved GiB-hour |
| Snapshots | Carry state past a session | Filesystem checkpoints; no memory | Pause and forks keep memory and processes |
| GPUs | Yes | Listed as coming soon | No |
| At once | Set by plan | 1,024 per account to start | 100 paid |
Training stacks
Modal's argument is one platform: GPU trainers and inference as functions, environments as sandboxes beside them. Prime's is the environment itself at scale and at a low price, with microVMs by the thousand on its own compute. Runtime is the environment layer too, billed by use. That suits rollouts that spend most of each step waiting for a policy model to answer.
Cost for the same job
The benchmark in full, 60 seconds a run (one physical core on Modal, Prime's 5 GiB disk):
- CPU
- 1,000 × 60 s × 1 core × $0.00003942
- $2.37
- Memory
- 1,000 × 60 s × 4 × $0.00000667
- $1.60
- 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
For a month of 100,000 runs: $396.60 on Modal, $151.67 on Prime, and $63.89 on Runtime. When both CPUs stay busy for the whole minute, the cost is $3.97 on Modal, $1.52 on Prime, and $1.33 on Runtime.
Which one to pick
- Modal when environments and GPU training should live in one platform.
- Prime Sandboxes for a thousand microVMs running at the same time inside Prime Intellect.
- Runtime for the lowest price per rollout, forks of a warmed-up environment with its memory, and Harbor and Inspect integrations for eval suites.
See Runtime vs Modal and Runtime vs Prime Sandboxes.
Runtime Cloud
Runtime costs 84% less than Modal and 58% less than Prime for rollouts that wait on a model. In the benchmark, 1,000 one-minute runs of a 2 vCPU, 4 GiB sandbox with 20 CPU-seconds of work each cost $3.97 on Modal, $1.52 on Prime, and $0.64 on Runtime.
Runtime bills measured CPU in a Firecracker microVM per sandbox. Start free with npx withruntime login. Use the migration guide for existing Modal code.
Sources
Modal rates were checked 25 October 2026. Prime rates were checked 25 October 2026.
- Modal pricing, Modal resources and billing
- Prime Sandboxes overview, Prime Sandboxes launch
- Runtime pricing
Facts on this page were checked on 26 October 2026.