We have users that login to our website. Once logged in they have the ability to shop our StoreFront. Once they find a product and continue to checkout, they are again presented with a login. /app/checkout/prepareLogin

Can we by-pass the login, use some kind of SSO , or utilize an API?

So, it doesn’t sound like we’re talking about anything to do with Infusionsoft until after the purchase. But the double login request is all happening on your website/shop. This means it really depends on what your using. I’m guessing it’s a Wordpress site. Are you using a membership plugin with a shopping cart plugin. For example, a common combination would be memberium or access ally with woocommerce?