[brooksmtownsend]

Containers take seconds to start so a container must always be running. Wasm starts in microseconds and most Wasm platforms scale to zero by default because they do not suffer from cold starts.

Wasm also offers incredible density characteristics. The same application hosted in a container has a much larger footprint than the Wasm equivalent, ~hundreds of MBs to GBs compared to a typical Wasm app that is typically <10MBs and often KBs. Wasm is based around a linear memory model such that it supports binpacking by the runtime. Where a system may be able to run hundreds of containers, thousands of Wasm instances can be run by a single Wasm runtime.

The typical cost savings for using a Wasm-based serverless platform vs a container-based one is significant. This is dependent on the language and workload, but I generally expect +30% efficiency.

Containers are not secure by default and are generally not considered an appropriate sandbox. Wasm was designed to run in the web where sandboxability is a critical requirement and first principle of the design. For serverless, this means a single Wasm host may be multi-tenant. This is why Fastly, Shopify, and Cloudflare use Wasm for serverless workloads ($$$ + safety).