I did something similar (though I used a slightly different method to intercept traffic) to make the US version of the Costco app better: www.97cost.co

I'm only surfacing two api requests that Costco's app is using, but even with a server as a middle man between the browser and Costo's backend this is way faster than the app.

Source: https://github.com/DavidZirinsky/costco-deals