What is Firecracker?

Firecracker makes virtual machines smaller by removing hardware emulation that short-lived server workloads do not need. Its microVMs use hardware virtualization and a separate guest kernel, addressing the shared-kernel boundary discussed in Browserbase's explainer.

The project documentation describes a minimal virtual-machine monitor built on Linux's KVM virtualization system. Fewer emulated devices reduce memory overhead and the amount of exposed functionality. That makes virtual-machine isolation more practical for running many small workloads, although the project's security model still depends on a correctly configured host.

“About 50,000 lines of Rust called Firecracker , which exists because the industry finally admitted that a Linux container that controls resource usage was never designed to be a security boundary.”

“One bug in any one of those syscalls and it's game over for every tenant on that machine.”

“For a web request that lives 40ms, you'd spend 40× that booting the machine.”

“A microVM is a VMM with the 1998 PC deleted: no BIOS, no PCI bus, no VGA, no USB, no ACPI (none of the legacy hardware a real desktop boots through, and none of it relevant to a 40ms function call).”