The **software carbon intensity (SCI)** of an application is the sum of its operational emissions and embodied hardware emissions. Serverless, or functions as a service (FaaS), provides a path towards reducing operational emissions by running event-driven applications only as needed.

First generation serverless technologies however have a few limitations that make them cumbersome, slow, and inefficient. The first is that they're often based on Containers or microVM's - while both of these are faster than traditional virtualisation, they take seconds-to-tens-of-seconds to start, and often require pre-warming to be performant. The second is that the developer experience is often poor, with local development often being an afterthought, instead pushing developers to deploy software as part of their testing process.

This presentation discusses why Wasm is the greenest and most cross-platform unit of compute for serverless applications, how that translates to efficiency at scale, while still retaining an incredible developer experience and simple operations. It will include a demo of how you can get started using serverless Wasm with Spin, an open source developer tool and take an application from your laptop to the cloud with Kubernetes. By the end of the talk, you'll have an understanding of the characteristics that make Wasm a cost-effective and sustainable unit for a greener cloud - and how you can deliver on those results without sacrificing developer experience.