Sandflare – I built a sandbox that launches AI agent VMs in ~300ms
TL;DR
Sandflare boots Firecracker microVMs for AI agents in ~300ms cold start — much faster than traditional VMs (5–10s) while providing real VM isolation instead of Docker's shared kernel.
Key Points
- The developer built it to safely run LLM-generated code in production, finding no existing tool that fit his needs.
- Built-in managed Postgres is wired into any sandbox with a single call, addressing the persistent-state requirement common to most agents.
- Current bottleneck toward the sub-100ms goal: Firecracker API initialization and network setup. Developer is seeking input from anyone who has pushed Firecracker further.
- Competitors include E2B, Modal, and Daytona; Sandflare differentiates on integrated Postgres and simpler pricing.
Nauti's Take
Sandflare is a solo project posted to Hacker News with one upvote and zero comments — so this is early-stage. But the problem framing is precise and honest: Docker's shared kernel is a genuine risk for untrusted code, and 5-second VM boots kill UX for synchronous agent workflows.
What stands out is that the developer isn't just shipping a sandbox demo — he's publicly asking for help pushing Firecracker below 100ms, which suggests real engineering depth over marketing polish. Whether Sandflare can compete with E2B and Modal ultimately depends on whether integrated Postgres and simpler pricing are enough of a wedge.
In this space, the tool that requires developers to think the least usually wins.
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