AWS Firecracker - Secure and fast microVMs for serverless computing

The c5, m5, t3, c5d, m5d, z1d, r5, r5d, m5a, r5a, a1, c5n, p3dn instance families all use the Nitro Hypervisor, which is based on Linux KVM code but offloading a lot of functionality to the Nitro System instead of using the normative QEMU setup.

Firecracker runs as a process in a customer-provided Linux 4.14 or newer kernel using the upstream KVM apis, that can be on an EC2 Metal Instance or on your own hardware.

Firecracker serves an entirely different purpose from Kubernetes. Kubernetes is a cluster scheduler but the containers being scheduled still need a runtime (typically Docker, containerd, or CRI-O) to execute the process within the container. These runtimes typically share a single Linux kernel instance and use the kernel cgroups feature to isolate workloads. In multi-tenant environments where each tenant is running unrestricted code this presents and unacceptably high security risk. If a hacker compromises one container and escapes the cgroup confinement they can potentially impact the security of other containers. Fargate is the building block for an alternative container runtime that uses extremely lightweight VMs and isolated kernel instances instead of the more traditional approach of sharing a kernel between all processes.

More broadly, that is exactly what AWS aims to do with serverless: "De-commoditize" its commoditization by containerization and tightly re-couple your application to AWS. Which is fine, if it suits someone to do that. AWS just likes to use different words to describe it: "Run code without thinking about servers" -- Which is actually only half the story, since you'll still be thinking about all that extra stuff, just that now you'll be thinking about AWS-specific versions of that stuff, in addition to paying the convenience fees.