A lot of shopify's engineering probably work on the back-end business logic for payment processing, sales tax, etc. Shopify has to comply with financial norms,

A lot of shopify's engineering probably work on the back-end business logic for payment processing, sales tax, etc. Shopify has to comply with financial norms, rule and laws in so many different jurisdictions. I know someone who works for Gusto (HR and payroll SaaS for small businesses)... most of their code-base is also business logic and whatnot for all the jurisdictions they support.