How can you make a store url dependent on environment

I'm sure I'm missing something discussed elsewhere...

Scenario:

In dev, I want all store proxies going to say localhost:3000/[specific-route]

In production, let's say it's http://ift.tt/1zhkYwo[specific-route]

I've hacked out solutions for this in the past outside of SA3, but hoping there's an easy way to do this, maybe through either systems env variables, or depending on whether running build for test vs production.

Yes, I can things closer by running my local service as localhost:3000/api, or I can wrangle something together using reverse proxies on each server... but I feel like there's something easy that I just keep missing.

Thanks

How can you make a store url dependent on environment