The compiler evaluates queries as much as possible at compile-time, so it is able to reduce `case` expressions, `let` expressions, etc. One neat outcome of this is that large expressions can sometimes be fully evaluated at compile-time, so they end up having no runtime cost at all!
I like this feature because it also only works because the query language is not Turing Complete. The design choices described in https://acadia.engineering/blog/solving-the-1-plus-N-query-p... that avoids 1+N patterns, also guarantees that queries terminate. This means they terminate whether you run them at runtime or at compile-time!
Anyway, the post also has an example app that uses https://github.com/acadia-engineering/elm-simple-server to run Elm code on the server, so maybe that is interesting as well.