Properly handling Shopify user authentication with other services

[sauzer77]

Hello , it's my first time posting here.

I have an existing site that I developed. It's both an e-commerce site and a content management site (LMS to be precise) in one monolithic site. I am looking to split this in 2 sites, so I can leverage Shopify for e-commerce, which will be hosted on the "www" subdomain, and the LMS will be hosted in the "platform" subdomain.

My issue is that I would like for my existing users to be able to login/register to my Shopify store (we use AWS Cognito for authentication) and I would like for the same user to have a seamless experience when going from a Shopify page to a page on my site. 

What is the Shopify tech stack I should be looking into for achieving this? 

Thanks so much for your help!

[magecomp]

Hello @sauzer77 

Honestly i am not sure if i understood your query completely but in shopify if you want to lock something behind the account login, you can use either locksmith or shoplock. https://apps.shopify.com/required-login-for-customers

[sauzer77]

Basically this is the behavior I am looking to achieve:

• User arrives at www.mysite.com which is a page served by Shopify
• user go in the login page and logs in. Here we are still in shopify, but I would like to use Cognito as an authentication service since all of my existing users are already there.
• If user is successfully authenticated, they are redirected to the shopify store page as a customer.
• Until now all normal except for using AWS Cognito. 
• Now user clicks on a link in the shopify store that takes them to platform.mysite.com (different service, different server).
• When the user lands on this page (remember different service and server), I would like him/her to be already authenticated and logged in, so going from one service to another is as seamless as possible. It basically needs to feel almost like the same website/service.

So my question is: how would I go about developing an app that can communicate with Cognito for authentication and authorization? Does it even have to be an app or can it be done in the theme itself? If an app is recommended, should it be a partner app even if I just need it to work with my store for this specific case?

It would be amazing if somebody here could give me a high level overview of what api I should use for the different stages of this development. 

Thanks so much!