Inside Replit's Sandbox Rewrite: From Linux Containers to MicroVMs
amasad · x · 2026-11-06
Replit published the first part of an engineering series on completely rewriting its sandbox engine—run for nearly a decade—from Linux containers to MicroVMs, now used by Agents that build applications without any coding.
Key points:
- Security motivation: OpenAI's Hugging Face incident and Anthropic's evaluation incidents showed autonomous agents can reach and harm real systems beyond their intended scope, demanding a stronger isolation boundary.
- The new engine delivers stronger isolation, bottomless storage, and cloud portability, powering Bring Your Own Cloud into customers' AWS/GCP/Azure environments.
- The migration was pulled off invisibly: hundreds of millions of projects moved smoothly with zero data loss.
- Part 2 will cover orchestrating tens of thousands of MicroVMs on Kubernetes.
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