Show HN: Sub-millisecond VM sandboxes using CoW memory forking

Sub-millisecond VM sandboxes for AI agents via copy-on-write forking

Try it

curl -X POST https://api.zeroboot.dev/v1/exec \ -H ' Content-Type: application/json ' \ -H ' Authorization: Bearer zb_demo_hn2026 ' \ -d ' {"code":"import numpy as np; print(np.random.rand(3))"} '

Benchmarks

Metric Zeroboot E2B microsandbox Daytona Spawn latency p50 0.79ms ~150ms ~200ms ~27ms Spawn latency p99 1.74ms ~300ms ~400ms ~90ms Memory per sandbox ~265KB ~128MB ~50MB ~50MB Fork + exec (Python) ~8ms - - - 1000 concurrent forks 815ms - - -

Each sandbox is a real KVM virtual machine with hardware-enforced memory isolation.

How it works

Firecracker snapshot ──► mmap(MAP_PRIVATE) ──► KVM VM + restored CPU state (copy-on-write) (~0.8ms)

Template (one-time): Firecracker boots a VM, pre-loads your runtime, and snapshots memory + CPU state Fork (~0.8ms): Creates a new KVM VM, maps snapshot memory as CoW, restores all CPU state Isolation: Each fork is a separate KVM VM with hardware-enforced memory isolation

SDKs

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