Dev tools · alternatives · 2026

24 alternatives to Sub-millisecond VM sandboxes using CoW memory forking

I wanted to see how fast an isolated code sandbox could start if I never had to boot a fresh VM. So instead of launching a new microVM per execution, I boot Firecracker once with Python and numpy already loaded, then snapshot the full VM state. Every execution after that creates a new KVM VM backed by a `MAP_PRIVATE` mapping of the snapshot memory, so Linux gives me copy-on-write pages automatically. That means each sandbox starts from an already-running Python process inside a real VM, runs the code, and exits. These are real KVM VMs, not containers: separate guest kernel, separate guest…

This project demonstrates a method for creating isolated code sandboxes that start in sub-millisecond time using Firecracker microVMs. Instead of booting a fresh VM for each execution, it snapshots a pre-loaded VM with… Below are 24 products that do a similar job, ranked by how close each is in meaning and then by launch-day votes.

1
Tiny VM sandbox in C with apps in Rust, C and Zig▲196
Minimalist, dependency-free virtual machine sandbox for microcontrollers and other resource-constrained devices. Single C file, no dynamic memory allocations, asynchronous design, pure C99 - ringtailsoftware/uvm32
Dec 2025 · github.com · its alternatives →
2
Smol machines – subsecond coldstart, portable virtual machines▲499
Branchable computing by using a portable, lightweight, self-contained virtual machine - smol-machines/smolvm
Apr 2026 · github.com · its alternatives →
3
Ephemeral VMs in 1 Microsecond▲84
Contribute to libriscv/drogon-sandbox development by creating an account on GitHub.
2024 · github.com · its alternatives →
4
AVR-VM – VM with JIT-compiler for ATMega32 written in Rust▲78
VM with JIT-compiler for ATMega32 written in Rust. Contribute to MackieLoeffel/avr-vm development by creating an account on GitHub.
2017 · github.com · its alternatives →
5
npm i -g hotcell▲97
Hi HN! Sina here. i wanted to share this open source project (apache 2.0) that i've been working on for the past month or so. it's called hotcell and it lets you create/pause/manage sandboxes on any device (your laptop, linux vm, bare metal). i've tested it against various benchmarks that i found on computesdk (https://www.computesdk.com/benchmarks/sandboxes/) as well as the one shared by dax (cofounder of open code) on twitter recently (link to his original thread and my reply https://x.com/sinasanm/status/2078158598996443346) and…
Aug 2026 · github.com · its alternatives →
6
Clone, a small Rust VMM, forks VMs in under 20ms via CoW▲11
We needed a secure, multi-tenant way to offer shell accounts to users, but most VMMs were using too much memory and containers are unsafe. With clone, VMs are now more memory efficient than containers in most cases. Since many other projects on HN looked like they were doing this too, open sourcing this was the right thing to do. Feel free to use in whole or in part as you see fit!
Apr 2026 · github.com · its alternatives →
7
The Cloud for AI Agents▲128
Spin up secure sandboxes in ~100 ms
Nov 2025 · hopx.ai · its alternatives →
8
A small virtual machine written in C▲212
"interesting" VM in C. Let's see how this goes. Contribute to tekknolagi/carp development by creating an account on GitHub.
2014 · github.com · its alternatives →
9
Zerobox – Sandbox any command with file, network, credential controls▲141
I'm excited to introduce Zerobox, a cross-platform, single binary process sandboxing CLI written in Rust. It uses the sandboxing crates from the OpenAI Codex repo and adds additional functionalities like secret injection, SDK, etc. Watch the demo: https://www.youtube.com/watch?v=wZiPm9BOPCg Zerobox follows the same sandboxing policy as Deno which is deny by default. The only operation that the command can run is reading files, all writes and network I/O are blocked by default. No VMs, no Docker, no remote servers. Want to block reads to /etc? zerobox…
Mar 2026 · github.com · its alternatives →
10
Forkrun – NUMA-aware shell parallelizer (50×–400× faster than parallel)▲151
forkrun is the culmination of a 10-year-long journey focused on "how to make shell parallelization fast". What started as a standard "fork jobs in a loop" has turned into a lock-free, CAS-retry-loop-free, SIMD-accelerated, self-tuning, NUMA aware shell-based stream parallelization engine that is (mostly) a drop-in replacement for xargs -P and GNU parallel. On my 14-core/28-thread i9-7940x, forkrun achieves: * 200,000+ batch dispatches/sec (vs ~500 for GNU Parallel) * ~95–99% CPU utilization across all 28 logical cores, even when the workload is non-existant (bash no-ops / `:`)…
Mar 2026 · github.com · its alternatives →
11
LocalGPT – A local-first AI assistant in Rust with persistent memory▲331
I built LocalGPT over 4 nights as a Rust reimagining of the OpenClaw assistant pattern (markdown-based persistent memory, autonomous heartbeat tasks, skills system). It compiles to a single ~27MB binary — no Node.js, Docker, or Python required. Key features: - Persistent memory via markdown files (MEMORY, HEARTBEAT, SOUL markdown files) — compatible with OpenClaw's format - Full-text search (SQLite FTS5) + semantic search (local embeddings, no API key needed) - Autonomous heartbeat runner that checks tasks on a configurable interval - CLI + web interface + desktop GUI - Multi-provider:…
Feb 2026 · github.com · its alternatives →
12
Whirlwind – Async concurrent hashmap for Rust▲140
Hey HN, this is Will and David from Fortress (https://news.ycombinator.com/item?id=41426998). We use a lot of async Rust internally, and created this library out of a need for an async-aware concurrent hashmap since there weren’t many available in the Rust ecosystem. Whirlwind is a sharded HashMap with a fully asynchronous API. Just as dashmap is a replacement for std::sync::RwLock, whirlwind aims to be a replacement for tokio::sync::RwLock. It has a similar design and performance characteristics to dashmap, but seems to perform better in read-heavy workloads with tokio's…
2024 · github.com · its alternatives →
13
krunvm – Create and run lightweight VMs from OCI images▲82
Create microVMs from OCI images. Contribute to slp/krunvm development by creating an account on GitHub.
2021 · github.com · its alternatives →
14
Katakate – Dozens of VMs per node for safe code exec▲124
I've built this to make it easy to host your own infra for lightweight VMs at large scale. Intended for exec of AI-generated code, for CICD runners, or for off-chain AI DApps. Mainly to avoid Docker-in-Docker dangers and mess. Super easy to use with CLI / Python SDK, friendly to AI engs who usually don't like to mess with VM orchestration and networking too much. Defense-in-depth philosophy. Would love to get feedback (and contributors: clear & exciting roadmap!), thx
2025 · github.com · its alternatives →
15
Kern – container and resource runtime in a 1.5 MB binary, no daemon▲70
A fast, rootless sandbox and virtual resource runtime for any workload, including untrusted and AI-generated code. Daemonless: a real, kernel-enforced container in ~3.5 ms from an OCI image, out of one static binary - getkern/kern
Aug 2026 · github.com · its alternatives →
16
A DOS-like hobby OS written in Rust and x86 assembly▲207
To try it out, simply build the project yourself from source, or use attached bootable ISO image of the system (in Releases on Github) and run it in QEMU. https://blog.vxn.dev/rou2exos-rusted-edition
2025 · github.com · its alternatives →
17
High-order Virtual Machine (HVM) – A Parallel Functional Runtime▲150
HVM1 (2022): a massively parallel, optimal functional runtime in Rust - HigherOrderCO/HVM1
2022 · github.com · its alternatives →
18
machine0 – Persistent NixOS VMs You Control from the CLI▲96
Hi HN! Excited to launch machine0, a CLI that makes it easy to create, provision and snapshot persistent NixOS (& Ubuntu) VMs. You can think of machine0 as a modern VPS provider. VMs stay on unless switched-off (with 99.99% uptime), they have static IPs and HTTPS endpoints, 1-60 vCPU, up to 240GB RAM and optionally GPUs. The CLI provides commands to manage lifecycle, snapshots and also provision the VMs using Nix flakes or Ansible playbooks. VMs are priced by the minute of usage. What makes machine0 unique is that it has first class support for NixOS! In a nutshell, NixOS lets you define…
Jun 2026 · machine0.io · its alternatives →
19
Slim 2: Create VM from Dockerfile, boots in seconds (+macOS M1/Hyper-V)▲59
Build and run tiny vms from Dockerfiles. Small and sleek. - GitHub - ottomatica/slim at 2.x
2022 · github.com · its alternatives →
20
microvm – a minimalist machine type for QEMU inspired by Firecracker▲145
2019 · github.com · its alternatives →
21
We built a <60ms, open-source alternative to E2B using RustVMM and KVM▲7
Over the past few months, as we scaled our internal AI Agents, we hit a dead end: Running LLM-generated arbitrary code in Docker is basically running naked on security due to container escape risks. But using full traditional VMs takes minutes to boot and eats too much memory to support high-density concurrency. We loved the developer experience of SaaS sandboxes on the market, but they are closed-source, expensive, and have too high a barrier to entry for self-hosting. So, our team decided to build our own. After months of grinding, using RustVMM and KVM, we built a blazing-fast,…
Apr 2026 · github.com · its alternatives →
22
I integrated my from-scratch TCP/IP stack into the xv6-riscv OS▲147
Hi HN, To truly understand how operating systems and network protocols work, I decided to combine two classic learning tools: the xv6 teaching OS and a from-scratch TCP/IP stack. I'm excited to share the result: my own from-scratch TCP/IP networking stack running directly inside the xv6-riscv (https://github.com/pandax381/xv6-riscv-net) kernel. The project uses a modern virtio-net driver, allowing it to run seamlessly in QEMU and communicate with the host machine. Key features: - From-Scratch Stack: The core is powered by microps…
2025 · github.com · its alternatives →
23
My microkernel-based OS built from scratch now has basic Unix commands▲69
This project contains no code from Linux, BSD, Minix, or any other OS. Everything up until this point is written entirely from scratch, including a pure microkernel (that only implements multiprocessor priority scheduling, memory management, and interprocess communication), a work-in-progress implementation of the standard C library, and a variety of servers that provide drivers and other essential OS functionality. At the time of writing this post, the servers provide drivers for the keyboard, NVMe SSDs (that works on real hardware), a Unix-like virtual file system (with a single root…
2024 · github.com · its alternatives →
24
Second State VM▲78
High performance secure & portable Rust functions in Node.js
2020 · secondstate.io · its alternatives →

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Ranked by how close each launch is in meaning, then by votes. Prices were read from each product’s own site when checked and can change. Refine with your own description →