Fly.io Machines vs Upstash Box

Fly.io Machines are microVMs for hosting your own apps in 17 regions: you bring the image, the tools and the agent. Upstash Box is built for agents: a ready container with a coding agent inside that pauses when idle and wakes on the next request, in the US only.

The companies and products

Fly.io Machines

Fly.io is an app hosting platform, and Machines are the microVMs underneath it that you can also start and stop through a REST API.

A Fly Machine boots your Docker image as a Firecracker microVM on Fly's own servers, in one of 17 regions. You pick a shared or performance CPU preset, attach at most one Volume for data that must last, and Fly Proxy can stop, suspend and wake Machines as traffic comes and goes. It is built for teams that host web apps and services worldwide; it is not a sandbox product, so this page compares the parts that overlap with agent work.

Kind of product: App hosting platform; Machines are its VM building block with a REST API
Isolation: Firecracker microVMs with hardware virtualization, on Fly's own servers
Regions: 17 regions in North America, Europe, Asia, Oceania, South America and Africa
CPU classes: Shared vCPUs guarantee 6.25% of each core with a burst balance; performance vCPUs get the full core
Storage: Root file system is ephemeral; one Volume of up to 500GB per Machine for lasting data
Free trial: 2 Machine hours or 7 days, up to 10 Machines of 2 vCPU / 4GB that stop after 5 minutes
Compliance: Lists SOC 2 Type II; a HIPAA package with a pre-signed BAA is sold as an add-on

Upstash Box

Upstash Box is a cloud computer for AI agents from Upstash, the company known for serverless Redis, Vector and QStash.

Each box is a Docker container with its own filesystem, shell, git and an optional coding agent such as Claude Code, Codex or OpenCode, which you drive from TypeScript or Python SDKs. A box pauses when it sits idle, keeps its files, and you pay for the CPU it actually uses. Upstash built it to run its own Context7 service and opened it to everyone in March 2026.

Isolation: One Docker container per box, with its own filesystem, process tree and network stack
Region: AWS us-east-1 only; more regions planned
Machine sizes: Small 2 vCPU / 4 GB / 5 GB disk, Medium 4 vCPU / 8 GB / 10 GB, Large 8 vCPU / 16 GB / 20 GB
Billing: Per active CPU hour by size, RAM not billed, storage per GB-month; keep-alive boxes at a flat monthly price
Concurrency: 10 boxes on Free, 1,000 on Pay as You Go, raised on request
Compliance: Upstash's trust center lists SOC 2 Type II, GDPR, HIPAA and DPF for the company

Which use cases each one fits

For each use case, Battleships prices every sandbox provider on the same workload and sorts them from the cheapest monthly bill up. “92nd cheapest of 367” means 91 of the other 366 providers run that workload, with every feature it needs, for less. “With limits” means the provider runs it but misses something, so it is listed after every full match. Open a use case for its whole ranking and what each provider misses.

Use case and its workload	Fly.io Machines: price rank	Upstash Box: price rank	boat: price rank
Software factory 100 at once · 4 vCPU / 8 GB · 2,200 sessions of 8 h a month A software factory needs Docker: on Fly you install it in your own image and keep files on a Volume, an Upstash box cannot run it, and boat has it ready.	92nd of 367, with limits $836 a month	61st of 367, with limits $464 a month	3rd cheapest of 367 $634 a month
Always-on AI employees 50 machines 24/7 · 2 vCPU / 4 GB	125th of 366, with limits $816 a month	103rd of 366, with limits $475 a month	5th cheapest of 366 $657 a month
Code interpreter bursts 100 at once · 1 vCPU / 2 GB · 200,000 sessions of 1 min a month Upstash fits short code runs fully, since an idle box costs no CPU and RAM is not billed, while Fly's cheapest rate needs a 1-year reservation.	75th of 345, with limits $94 a month	10th cheapest of 345 $119 a month	186th of 345, with limits $2,000 a month
Sandboxes for your users 300 at once · 2 vCPU / 4 GB · 30,000 sessions of 23 min a month boat ranks first and Upstash is close behind, since it wakes a user's paused box on the next request; Fly's API creates about one Machine per second per app.	69th of 361, with limits $600 a month	2nd cheapest of 361 $222 a month	Cheapest of 361 $209 a month
RL rollouts 1,000 at once · 2 vCPU / 4 GB · 1,000,000 sessions of 3 min a month Fly does far better than Upstash for RL rollouts, with per-second billing and Docker you can install in your own image.	48th of 360, with limits $2,838 a month	352nd of 360, with limits $8,068 a month	34th of 360, with limits $2,000 a month
Agent evals 250 at once · 4 vCPU / 8 GB · 15,000 sessions of 20 min a month	117th of 364, with limits $457 a month	52nd cheapest of 364 $1,011 a month	10th cheapest of 364 $200 a month
CI runners 40 at once · 8 vCPU / 16 GB · 6,000 sessions of 12 min a month CI jobs that build containers need Docker, which an Upstash box lacks, and they drain a shared Fly vCPU's burst balance; boat has Docker and /dev/kvm on one CPU class.	152nd of 377, with limits $288 a month	120th cheapest of 377 $1,520 a month	4th cheapest of 377 $86 a month
24/7 dev boxes 1 machine 24/7 · 4 vCPU / 8 GB Upstash's keep-alive box is a cheap flat-price dev box; boat's is a full VM with Docker, root and a 50 GB disk.	118th of 368, with limits $53 a month	10th cheapest of 368 $20 a month	18th cheapest of 368 $26 a month
Computer-use agents 50 at once · 4 vCPU / 8 GB · 20,000 sessions of 15 min a month Neither Fly nor Upstash has a desktop: Fly leaves it to your image and Upstash's browser is headless, while boat streams a Linux desktop at 60fps.	95th of 369, with limits $173 a month	73rd of 369, with limits $76 a month	6th cheapest of 369 $200 a month
Browser-use agents 50 at once · 2 vCPU / 4 GB · 30,000 sessions of 10 min a month	160th of 367, with limits $90 a month	49th of 367, with limits $38 a month	7th cheapest of 367 $200 a month
Scraping & bots (startup scale) 50 at once · 1 vCPU / 2 GB · 100,000 sessions of 3 min a month	161st of 346, with limits $67 a month	37th cheapest of 346 $400 a month	6th cheapest of 346 $90 a month
Mass scraping & bots (undetectable) 1,000 at once · 1 vCPU / 2 GB · 3,000,000 sessions of 2 min a month Fly does much better than Upstash for mass scraping, since it can spread scrapers across 17 regions while Upstash runs only in AWS us-east-1.	44th of 338, with limits $1,232 a month	200th of 338, with limits $8,000 a month	71st of 338, with limits $1,800 a month
Parallel red teaming 200 at once · 2 vCPU / 4 GB · 5,000 sessions of 30 min a month	118th of 360, with limits $63 a month	225th of 360, with limits $259 a month	2nd cheapest of 360 $200 a month
GPU eval jobs 10 at once · 8 vCPU / 32 GB · 500 sessions of 30 min a month	Can't run it	Can't run it	Can't run it
macOS agents 5 at once · 4 vCPU / 8 GB · 1,000 sessions of 20 min a month	Can't run it	Can't run it	Can't run it

Key features

Feature	Fly.io Machines	Upstash Box	boat
Kind of product	App hosting platform; you boot your own image as a microVM through a REST API	Agent sandbox: a ready box with a shell, git and an optional coding agent	Agent sandbox: a full VM per agent, ready to use
Isolation	Firecracker microVM with its own kernel, on Fly's own servers	One Docker container per box, on AWS	Full VM with its own kernel on dedicated AMD Ryzen 9 9950X (Zen 5) hosts
Docker inside	Yes, with root, if you install it in your image; Fly's own init, no systemd	Not documented; the box is itself a container, and custom images are listed as coming soon	Docker, root and systemd ready on every machine
Nested virtualization	No /dev/kvm	No VM support documented	/dev/kvm for Android emulators and nested VMs
Files after a stop	Root file system is ephemeral; lasting data goes on one Volume, billed for its full size around the clock	A paused box keeps its files; storage keeps billing while paused	The whole disk is kept, saved every minute and on stop; a stopped sandbox costs nothing
Disk size	One Volume of up to 500GB per Machine	5, 10 or 20 GB by box size	50 GB at the default 4 vCPU / 8 GB size, 12 to 251 GB by size
Idle and wake	Fly Proxy stops or suspends idle Machines and wakes them on a request; suspend keeps memory up to 2GB	A box pauses when idle and a request to its public URL resumes it	Started and stopped through the API; resume reboots from disk
Fork	Clone copies a Machine's config; a cloned Volume starts empty	Snapshot a running box and start many new boxes from it	Fork a running sandbox, disk included
Desktop and browser	None built in; you add them to your own image	Managed headless Chromium with AI page actions and CDP; no desktop	Linux desktop streamed at 60fps, Chromium, computer use and browser control
Coding agents	None built in; you install and run agents yourself	Claude Code, Codex and OpenCode built in, with run and stream APIs, webhooks and scheduled prompts	Claude Code, Codex, OpenCode and more preinstalled, with a prompt, steer and events API
Keeping keys out of the sandbox	Secrets arrive as environment variables; Fly's open-source tokenizer proxy can be deployed yourself	Host proxy injects headers into outbound HTTPS on port 443, set when the box is created	AI credentials proxy for model providers and any HTTPS API; switch a credential to another account when credits run out
Outbound rules	Network policies allow chosen ports and protocols and deny the rest	Allow all, deny all, or allow and deny by domain and CIDR, changeable on a running box	Open internet on every plan; no provider-side allowlist
CPU	Shared vCPUs guarantee 6.25% of a core plus bursts; performance vCPUs get the full core at a higher rate	Billed per active CPU hour by box size; RAM not billed	One CPU class on every plan, with no baseline quota or burst balance
Regions	17 regions on six continents	US only (AWS us-east-1)	EU only: Germany, Finland, France

Every feature Battleships tracks (43)

Feature	Fly.io Machines	Upstash Box	boat
Full VM (own kernel)	Yes	No	Yes
Docker inside	Yes	No	Yes
Nested virtualization	No	No	Yes
Root	Yes	Not published	Yes
Systemd	No	Not published	Yes
Desktop GUI	No	No	Yes
Browser	No	Yes	Yes
Computer-use API	No	No	Yes
SSH	Yes	Yes	Yes
Persistent disk	Yes	Yes	Yes
Pause/resume	Yes	Yes	Yes
Automatic snapshots	Yes	No	Yes
Fork/clone	Yes	Yes	Yes
Live fork (no pause)	Yes	Yes	Yes
Memory fork	No	No	No
Custom image (Docker or snapshot)	Yes	Yes	Yes
≥24 h sessions	Yes	Yes	Yes
Idle auto-stop	Yes	Yes	No
Wake on request	Yes	Yes	No
HTTPS preview URLs	Yes	Yes	Yes
Raw TCP inbound	Yes	No	Yes
Public IPv4	Yes	No	No
Egress allowlist	Yes	Yes	No
Secret proxy	No	Yes	Yes
Secret proxy for any API	No	Yes	Yes
Preinstalled agents	No	Yes	Yes
Agent harness API	No	Yes	Yes
MCP server	Yes	Yes	No
GPU	No	No	No
Windows	No	No	No
Arm64	No	Yes	No
Self-hosting	No	No	No
BYOC	No	No	No
Open source	Yes	No	No
Scoped API keys	Not published	Not published	Yes
Spend limits	No	Not published	Yes
Usage per sandbox (API)	No	Yes	Yes
Audit logs	Not published	Not published	No
SSO	No	No	No
SOC 2	Yes	Yes	No
HIPAA	Yes	No	No
EU data residency	Yes	No	Yes
Zero data retention	Not published	Not published	Yes

Performance

Fly.io MachinesNot measured

Upstash BoxNot measured

boat26.69 runs/s

There is no comparable measurement for either: neither Fly.io Machines nor Upstash Box was part of the public StarSling run where boat did 26.69 Node.js build-and-test runs per second at 4 vCPU / 8 GB. On Fly, speed depends on the CPU class, since shared vCPUs guarantee only 6.25% of a core and get throttled under long load.

Node.js build-and-test loop at 4 vCPU / 8 GB, higher is better. Measured with the open hpc-sandbox-benchmarks suite. Fly.io Machines and Upstash Box have no published run in this suite yet, so there is no like-for-like number to compare.

Pricing in five scenarios

Each bill is priced from the providers' public price lists by the open Battleships engine, with the cheapest plan that runs the scenario.

Scenario	Fly.io Machines, a month	Upstash Box, a month	boat, a month
One coding agent, workdays 4 vCPU / 8 GB, 50 GB disk, 8 hours a day, 22 days a month, files kept between days	$15 · Pay As You Go · with limits	$21 · Pay as You Go	$20 · $20/mo
One agent that never stops 4 vCPU / 8 GB, 50 GB disk, running 24/7 all month	$36 · Pay As You Go · with limits	$21 · Pay as You Go	$26 · $20/mo
50 agents in parallel 50 machines of 4 vCPU / 8 GB at once, 8-hour sessions, 1,100 sessions a month, Docker inside	$487 · Pay As You Go · with limits	$900 · Pay as You Go · with limits	$317 · $20/mo × 3 seats
Sandboxes for your users 2 vCPU / 4 GB, 30,000 sessions of 10 minutes a month, up to 300 at once	$110 · Pay As You Go · with limits	$306 · Pay as You Go	$200 · $100/mo × 2 seats
1,000 short jobs at once 2 vCPU / 4 GB, 1,000 at once, 3 minutes each, 200,000 jobs a month	$232 · Pay As You Go · with limits	$1,822 · Pay as You Go	$2,000 · $2000/mo · with limits

Fly.io Machines: Fly bills each Machine per second while it runs, by CPU preset and memory, with no plan fee; Volumes are billed for their full size all month. The figures here use shared vCPUs bought in 1-year reservation blocks for 40% off.

Upstash Box: A standard box is billed for the CPU it actually uses, at $0.10, $0.20 or $0.40 per active CPU hour by size, plus $0.10 per GB-month of storage, and RAM is free. A keep-alive box costs a flat $8, $16 or $32 a month.

Upstash Box: You pick a monthly plan from $20, and all of it becomes usage credit spent per second on running sandboxes. A stopped sandbox costs nothing and keeps its disk.

Limits in those scenarios

Fly is marked a compromise in all five scenarios: it is an app platform, its lowest figures need a 1-year reservation, and its shared vCPUs guarantee only 6.25% of each core, so long builds get throttled. Upstash fits four of the five, but the 50-agent scenario fails because a box cannot run Docker, and its egress price is not published. On boat, 1,000 short jobs at once are queued by start limits even on the $2,000 plan.

Scenario	Fly.io Machines	Upstash Box	boat
One coding agent, workdays	different kind of product: app platform 1-year commitment burstable CPU: 6.25% of each vCPU guaranteed, throttled above that	flat pool: the tier is billed whether used or not egress price not published	None that bite
One agent that never stops	different kind of product: app platform 1-year commitment burstable CPU: 6.25% of each vCPU guaranteed, throttled above that	flat pool: the tier is billed whether used or not egress price not published	None that bite
50 agents in parallel	different kind of product: app platform 1-year commitment burstable CPU: 6.25% of each vCPU guaranteed, throttled above that	missing Docker inside flat pool: the tier is billed whether used or not egress price not published	None that bite
Sandboxes for your users	different kind of product: app platform 1-year commitment burstable CPU: 6.25% of each vCPU guaranteed, throttled above that	egress price not published	None that bite
1,000 short jobs at once	different kind of product: app platform 1-year commitment burstable CPU: 6.25% of each vCPU guaranteed, throttled above that	egress price not published	max 2,400 starts/day (needs ~6,667) max 600 starts/hour (needs ~1,000) bursts above 90 starts/min are queued (a burst of 333 takes ~4 min to start)

Which one should you use?

Use Fly.io Machines when

you want to boot your own image near users in many regions, host full apps next to your sandboxes, or need big Volumes.

17 regions worldwide. Useful when agents or users sit far apart: Fly runs Machines in 17 regions, from the US to Sydney and Johannesburg.
Your own image, with a full app platform. Useful if you host whole apps: you boot any Docker image, with private networking, Anycast IPs, custom domains and raw TCP.
Big disks and memory suspend. Useful for data-heavy work: a Volume holds up to 500GB, and small Machines suspend with their memory kept.

Use Upstash Box when

you want a coding agent running today in a light box that pauses when idle, wakes on a request, and runs in the US.

Coding agents built in. Useful if you want agents running today: Claude Code, Codex and OpenCode ship in every box with SDKs and webhooks.
Idle costs no CPU. Good for agents that wait a lot: you pay only for CPU actually used, RAM is free, and a request wakes the box.
Domain-level outbound rules. Useful when an agent may only reach a short list of domains or IP ranges, changeable on a running box.

Where boat fits

Fly gives you a fast microVM but leaves the sandbox for you to build, and Upstash gives you a ready agent box that is only a container. If your agents need a real machine with Docker, a desktop and a disk that keeps everything, boat gives you that ready on every machine.

A full VM with Docker and /dev/kvm

An Upstash box is itself a container, so an agent cannot run a database in Docker or boot an emulator. On Fly you add Docker to your own image, with no systemd and no /dev/kvm.

A disk that keeps everything

A Fly Machine's root file system is ephemeral, so the agent's tools and caches need a Volume billed for its full size around the clock. Upstash keeps files but stops at 20 GB, and storage bills while paused.

A desktop and agents driven from outside

boat streams a 60fps desktop with Chromium and computer use, and you drive agents inside from outside with a prompt, steer and events API. Upstash's browser is headless, and on Fly you build all of it yourself.

Use boat when your agents need a real machine for hours: Docker, emulators, a desktop, coding agents driven from outside and a disk that survives every stop. Compare it one to one: boat vs Fly.io Machines and boat vs Upstash Box.

Questions people ask

Is Fly.io Machines cheaper than Upstash Box?

Often, if you use Fly's cheapest rate, shared vCPUs on a 1-year reservation. One coding agent on workdays is $15 a month on Fly and $21 on Upstash, and 300 user sandboxes are $110 versus $306. One agent that never stops is cheaper on Upstash: $21 against $36 on Fly.

Which is faster, Fly.io Machines or Upstash Box?

Neither has a result in the StarSling CPU benchmark, so there is no fair comparison. Fly's shared vCPUs guarantee only 6.25% of a core and get throttled under long load, while its performance vCPUs get the full core at a higher rate.

Can Fly.io Machines or Upstash Box run Docker?

A Fly Machine is a microVM with root, so you can install and run Docker inside your own image. Upstash's docs do not offer Docker inside a box, since each box is itself a container. boat has Docker, systemd and /dev/kvm ready on every machine.

Do they keep my files when they stop?

On Fly, only what sits on a Volume, since the root file system is ephemeral. An Upstash box keeps its files while paused, with storage still billed, on a disk of 5 to 20 GB. boat keeps the whole disk, saved every minute and on stop.

Which one has coding agents built in?

Upstash Box ships Claude Code, Codex and OpenCode with run and stream APIs. Fly has none built in, so you install and drive agents yourself. boat preinstalls them with a prompt, steer and events API.

Where do Fly.io Machines and Upstash Box run?

Fly runs Machines in 17 regions on six continents. Upstash Box runs only in AWS us-east-1, with more regions planned. boat runs in the EU, in Germany, Finland and France.

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