Which is better, Fly Machines or Northflank?
It depends on how busy the CPU is and where the work must run. For agents that sit idle between model calls, Runtime has the lowest bill: $0.64 for 1,000 one-minute runs, against $1.11 on Northflank and $1.53 on Fly Machines, since it bills the CPU used. Pick Northflank for jobs that keep every CPU busy, where its rate is lowest, for GPUs, or for your own cloud account. Pick Fly Machines for a service near its users, with Fly Volumes and Managed Postgres.
At a glance
Fly Machines are priced at the Ashburn (iad) rates. Northflank's
isolation and regions are from its sandbox page, read 26 October 2026.
| Fly Machines | Northflank | Runtime | |
|---|---|---|---|
| Isolation | Firecracker microVM | microVMs for CPU workloads, gVisor for GPU workloads | Firecracker microVM, own kernel |
| CPU | Inside a fixed size, billed while started | $0.01667 per allocated vCPU-hour | $0.025 per vCPU-hour of measured CPU, with a small floor |
| Memory | Inside the size; more at $6 per GB per month | $0.00833 per GB-hour | $0.0075 per reserved GiB-hour |
| 2 vCPU, 4 GB | performance-2x, $0.0916704 an hour |
$0.0667 an hour | $0.08 an hour fully busy, $0.03125 waiting |
| Where it runs | 17 Fly regions | 5 Northflank regions, or your AWS, GCP, Azure or Oracle | Runtime's dedicated servers |
| Plan fee | None; pay as you go | None published for compute | None; prepaid credit from $10 |
| Free start | Not stated on the pricing page | 2 services, 2 jobs and 1 database free | 100 free hours of a 1 GB machine in the first 30 days, no card |
| Sandbox model | A Machine, created through the Machines API | A service with a deployment plan | A sandbox, created in one call |
Which is cheaper for a machine that is always busy?
Northflank. Its allocated rates put 2 vCPUs and 4 GB at $0.0667 an hour
(2 × $0.01667 plus 4 × $0.00833), against $0.0916704 for a Fly performance-2x
with 4 GB. It is also below Runtime's $0.08 an hour for the same size with
both CPUs working the whole time. For a build farm or a batch job that keeps
every core busy, Northflank's rate card is the lowest of the three.
The order changes as soon as the work waits. Fly and Northflank both bill a held vCPU the same whether it computes or idles on a model's reply. Runtime bills measured CPU, so the same sandbox waiting costs $0.03125 an hour: memory plus a floor of a twentieth of a vCPU. Most agent runs spend most of their time waiting.
A Fly performance vCPU is a whole core kept for the Machine. Runtime's default
CPU is shared. Set cpu: "reserved" to keep every vCPU for you when a job needs
it.
Cost for the same job
1,000 runs of a 2 vCPU, 4 GiB sandbox (4 GB on Fly and Northflank). Each run lasts 60 seconds and keeps the CPU busy for 20 CPU-seconds: an agent that mostly waits for a model.
- Size
- 1,000 × 60 s / 3,600 × $0.0916704
- $1.53
- CPU
- 1,000 × 60 s / 3,600 × 2 × $0.01667
- $0.556
- Memory
- 1,000 × 60 s / 3,600 × 4 × $0.00833
- $0.555
- CPU
- 1,000 × 20 s / 3,600 × $0.025
- $0.14
- Memory
- 1,000 × 60 s / 3,600 × 4 × $0.0075
- $0.50
At 100,000 runs per month, the cost is $152.78 on Fly Machines, $111.10 on Northflank and $63.89 on Runtime. With both CPUs busy for the whole minute, the job costs $1.11 on Northflank, $1.33 on Runtime and $1.53 on Machines. Northflank costs less than Runtime for work that never waits. Plan fees, storage, network and free allowances are left out.
Where can each one run?
Fly Machines run in 17 regions on Fly's own hardware, which suits an app that serves users worldwide. Northflank lists US West, US Central, US East, EU West and Asia East. It can run its sandboxes inside your own VPC on AWS, GCP, Azure or Oracle, with GPUs up to H100 in the same platform. Runtime runs every sandbox on dedicated servers it operates, each in a Firecracker microVM with its own Linux kernel. See security and Kata Containers vs Firecracker.
Which one to pick
- Pick Fly Machines for an app or service that should run near its users, with Fly Volumes and Managed Postgres beside it.
- Pick Northflank for jobs that keep every CPU busy, for GPUs, or to run sandboxes in your own cloud account.
- Pick Runtime for agents that wait on a model: measured CPU, pause that keeps memory and processes while you have credit, forks of a running sandbox, and one call to create a sandbox, with no service or deployment plan.
Runtime Cloud
For an agent that mostly waits, Runtime runs the same job for 58% less than a Fly Machine and 42% less than Northflank. 1,000 one-minute runs of a 2 vCPU, 4 GiB sandbox cost $1.53 on Fly Machines, $1.11 on Northflank and $0.64 on Runtime, because Runtime bills the CPU your code uses rather than the CPUs it holds. Rates checked 25 October 2026.
Every sandbox is its own Firecracker microVM, with no plan fee. Start free with npx withruntime login, and use the migration guide for code you already run.
Switch from either one
A sandbox is one call, with no app, service or deployment to set up first:
Pythonfrom withruntime import Sandboxwith Sandbox.create() as sbx: sbx.files.write("/workspace/invoice.py", "print(sum([125, 250, 375]))\n") run = sbx.exec(["python3", "/workspace/invoice.py"], timeout_ms=120_000) print(run.exit_code, run.stdout)Or give your coding agent the one instruction in migration. It
switches the project on a branch, tests it on the free usage, and reports the
saving per month. npx withruntime compare --from fly-machines (or
--from northflank) prices what you ran at the old provider's rates. Credit you add within 30 days of signing up is matched, up to $1,000 in total. The full side-by-sides are
Runtime vs Fly.io and
Runtime vs Northflank.
Sources
Fly.io prices checked 25 October 2026.
Rates checked 25 October 2026. The Northflank sandbox page was read 26 October 2026.
- Fly.io pricing, Machine CPU performance, Fly.io regions
- Northflank pricing, Northflank sandboxes, Sandboxes on Northflank
- Runtime pricing and security
Facts on this page were checked on 26 October 2026.