How to Implement a Secure Central Authentication Service in Six Steps - Shopify

This post details the six-step process for implementing the centralized authentication service (Identity) at Shopify. It covers synchronizing data from existing user accounts into the Identity service, routing all authentication through the Identity service via OpenID Connect (OIDC), prompting users to combine their multiple legacy accounts into a single Identity account, encouraging users to enable two-factor authentication (2FA), creating the combined Identity account within a single database transaction, and preventing the creation of new legacy accounts. It also elaborates on the user experience and technical challenges of account merging, including handling unverified email addresses and 2FA requirements.