AWS Lambda MicroVMs are a new compute primitive using Firecracker virtual machines for running untrusted or agent-generated code in fully isolated environments. Each MicroVM has its own kernel and hardware-enforced hypervisor boundary, supports full container workloads, near-instant startup from snapshots, and sessions lasting up to 8 hours. The Serverless Framework v4.39.0 introduces a new `sandboxes` top-level property in `serverless.yml` that provisions MicroVMs with minimal config — handling IAM roles, networking, logging, and dashboards automatically. A local emulator (`serverless dev --sandbox`) runs the same Docker image locally with real IAM emulation, eliminating deploy-to-test cycles. Built-in observability includes CloudWatch log groups, error metrics, dashboards, and configurable alarms. Three ready-to-deploy examples are available in the official examples repository.
