spin-fileserver VS spin-trigger-sqs

The handler functions can perform operations such as fetching data from external APIs, serving files, connecting to databases (such as relational databases, or Redis), or persisting state using Spin's built-in key/value storage.

We made that choice primarily because we want to leverage the really good startup times for Wasm (and in particular for Wasmtime), and not running any guest code (in this case, business logic) until there is an actual incoming request means the server can execute other applications while idle.

Now, HTTP workloads are not the only type of workloads that Spin can handle — because of the way it's built, it's entirely pluggable and you can build your own trigger (for example https://github.com/fermyon/spin-trigger-sqs), and potentially have long-running processes, but that is not currently possible with Spin today.

We are particularly excited about upcoming work to build external queue triggers, such as the experimental AWS SQS trigger. Once stabilized, with the plugin installed, spin up will be able to start an application that is triggered on new messages with specific attributes on a given queue.