Firecracker is a lightweight virtual machine monitor (VMM) designed to efficiently manage microVMs using Linux kernel-based virtual machines (KVM), offering a secure, multi-tenant environment for serverless workloads. Its minimalist design, which is only 4% the size of its traditional counterpart QEMU, reduces the attack surface and enhances security through features like the "jailer" that enforces security boundaries using Linux cgroups. Firecracker boasts rapid startup times of 125 milliseconds and supports high microVM creation rates, allowing thousands of microVMs to run concurrently with minimal overhead. As an open-source technology under the Apache 2.0 License, Firecracker is integrated into the container ecosystem, enabling interoperability with container services and promoting efficient resource distribution. This integration allows for the combination of the isolation and security of full virtualization with the speed and density of container technology, transforming serverless workload management.