AWS Serverless: Deep Dive into Lambda and Firecracker

AWS Lambda abstracts infrastructure, but under the hood, it relies heavily on Firecracker microVMs. Firecracker uses the KVM (Kernel-based Virtual Machine) to provision and manage secure, lightweight microVMs. A microVM has a minimal device model, stripping away unnecessary hardware emulation to achieve boot times of <125ms and a memory footprint of <5MB per VM.

When a Lambda function is invoked for the first time (a cold start), the Firecracker hypervisor allocates a new microVM. The control plane downloads the function package, initializes the language runtime, and executes the user's initialization code.

%%{init: {"theme": "default", "flowchart": {"useMaxWidth": true}}}%%
flowchart TD
    subgraph CPControlPlane ["Control Plane<br><br><br>"]
        A[API Gateway] -->|"Invoke()"| B[Worker Node]
    end
    subgraph VMFirecrackermicroVM ["Firecracker microVM<br><br><br>"]
        B --> C[MicroVM Init]
        C -->|"LoadRuntime()"| D[Language Runtime]
        D -->|"ExecuteHandler()"| E[Function Code]
    end