WebAssembly and Unikernels: A Comparative Study for Serverless at the Edge

Abstract: Serverless computing at the edge requires lightweight execution environments to minimize cold start latency, especially in Urgent Edge Computing (UEC). This paper compares WebAssembly and unikernel-based MicroVMs for serverless workloads. We present Limes, a WebAssembly runtime built on Wasmtime, and evaluate it against the Firecracker-based environment used in SPARE. Results show that WebAssembly offers lower cold start times for lightweight functions but suffers with complex workloads, while Firecracker provides higher, but stable, cold starts and better execution performance, particularly for I/O-heavy tasks.