I recently wrote a city -> geo lookup API for typeahead. Running on edge it's wicked fast. The database just barely fits in a CF worker though.

It’s all about latency. Even simple dynamically rendered websites can be much faster when you avoid multiple roundtrips to a far away DC.

If your pages depend on data from APIs that are not globally distributed, having an edge runtime can be worse. Specially when dealing with non distributed databases.

If you want to avoid super slow starts for an app that has some secret keys / other backend logic while staying on a free tier

I used it before for a simple geolockup service for a autocomplete.