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

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

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))"}'

| 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.

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 stateFork(~0.8ms): Creates a new KVM VM, maps snapshot memory as CoW, restores all CPU stateIsolation: Each fork is a separate KVM VM with hardware-enforced memory isolation

Python — sdk/python

from zeroboot import Sandbox
sb = Sandbox("zb_live_your_key")
result = sb.run("print(1 + 1)")

TypeScript — sdk/node

import { Sandbox } from "@zeroboot/sdk";
const result = await new Sandbox("zb_live_your_key").run("console.log(1+1)");

Working prototype. The fork primitive, benchmarks, and API are real, but not production-hardened yet. Open an issue if you're interested.