Fly Machines vs Blaxel pricing, idle costs and limits

Which is better, Fly Machines or Blaxel?

It depends on how much time your sandboxes spend idle rather than busy. Runtime costs the least either way: $0.64 for an agent that waits on a model, against $1.53 on a Machine and $3.45 on Blaxel, and less than both with the CPUs busy too. You set CPU and memory separately. Pick Fly Machines for general VMs in 17 regions with volumes and Managed Postgres. Pick Blaxel for sandboxes that idle free and wake in about 25 ms, or fleets over 100,000.

At a glance

The Machine is a performance-2x with 4 GB, at the rates of Fly's Ashburn (iad) region.

Which one costs less when the agent sits idle?

Blaxel, because it stops charging by itself. A Blaxel sandbox goes to standby about 15 seconds after its last connection closes, with no memory charge there, only the snapshot's storage. Reconnecting brings it back in under 25 ms with its files and running processes. Blaxel notes that external connections, such as database connections, message queues and HTTP pools, are not kept.

A Fly Machine bills its whole size for every second it is started. To stop paying, stop it, and a stopped Machine costs storage only; but a stop resets its root filesystem, so files that must last go on a Fly Volume. Suspend keeps memory and resumes in a few hundred ms, at the same storage-only cost, but Fly lists 2 GB of memory or less as a requirement, so the 4 GB Machine priced here cannot use it.

While it runs, the Machine is the cheaper of the two: $1.53 against $3.45 for the job below. The answer turns on how long each sandbox sits idle before you stop it, and whether memory has to survive.

Cost for the same job

1,000 runs of a 2 vCPU, 4 GiB sandbox (4 GB on Blaxel and the Machine). Each run lasts 60 seconds and keeps the CPU busy for 20 CPU-seconds: an agent that mostly waits for a model.

At 100,000 runs per month that is $152.78 on Machines, $345.00 on Blaxel and $63.89 on Runtime. With both CPUs busy for the whole minute, it is $1.33 on Runtime against $1.53 on Machines and $3.45 on Blaxel, so Runtime is cheaper however busy the sandbox is. The Machine figure assumes each Machine is stopped when its run ends, and the Blaxel figure includes the 15 seconds or so each sandbox stays billed before standby, $0.69 per 1,000 runs. Storage, network, plan fees, taxes and free credit are left out.

Pause and wake on Runtime

A Runtime sandbox pauses when you call pause(), or by itself after idle_pause_seconds with no request. Compute billing stops, memory and files are kept, and the sandbox wakes on the next request, or when you call wake(), from any process:

Pythonfrom withruntime import Sandboxsbx = Sandbox.create(timeout_seconds=600)sbx.exec("echo state > /workspace/state.txt")sbx.pause()  # memory and files are kept; compute billing stopsagain = Sandbox.connect(sbx.id)again.wake(timeout_seconds=1200)again.stop()

See how to pause and resume a sandbox and what a cold start is.

Which one to pick

• Pick Fly Machines for general-purpose VMs in 17 regions, up to 16 performance vCPUs and 128 GB, with volumes and Managed Postgres in the same account, or for CPU-bound jobs at a flat hourly price.
• Pick Blaxel for sandboxes that idle for free and come back in about 25 ms, or very large fleets: its top tier runs over 100,000 sandboxes concurrently.
• Pick Runtime for the lowest bill of the three at any load, CPU and memory chosen separately, and paused sandboxes kept with their memory at $0.08 per GB-month.

Switch from either one

From Machines, if you create a Machine for each job through the Machines API, create a Runtime sandbox instead and stop it when the job ends. From Blaxel, change @blaxel/core to withruntime/blaxel (Python: blaxel.core to withruntime.blaxel) and the code runs on Runtime; standby maps to automatic wake, which is on by default, so a request to a paused sandbox wakes it.

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 monthly saving. Credit you add within 30 days of signing up is matched, up to $1,000 in total. The full comparisons are Runtime vs Fly.io and Runtime vs Blaxel; Blaxel against Cloudflare is in Cloudflare Sandbox vs Blaxel.

Sources

Fly.io prices checked 25 October 2026.

Fly rates checked 25 October 2026 and its suspend page read 26 October 2026. Blaxel rates checked 25 October 2026, with its pricing page and sandbox documentation.

• Fly.io pricing, Machine suspend and resume, Fly Volumes, Fly.io regions
• Blaxel pricing, Blaxel sandboxes
• Runtime pricing

Facts on this page were checked on 26 October 2026.