[isoskeles]

Maybe not that helpful of an addition, but the most surprising thing I found was that Shopify has an option for an "app proxy", in which you can have some separate, custom web server that gets proxied through your Shopify store.

I've used this to some success in building a more robust product customization app (with functionality very specific to our business), more so than what I could find on their store. The biggest con for using the app proxy is around authentication. You can't do much special stuff with auth, basically the simplest option is to just wrap your proxied pages in a liquid check for customer.id. (Although, I can see this as a pro rather than a con, as it forces you to keep the proxy app simple.)

My biggest worry is one day Shopify just decides to discontinue app proxies. It doesn't seem like an option they try to point developers toward, so I don't trust it and am thinking about building on top of their API to avoid this.