There is a new trend of moving away from classic monolithic CMS architectures to more independent and abstract ones – headless CMS. It might seem like we no longer need to write a single line of code on the backend to build big and robust sites. Or like we no longer need to take care of the server, scaling, security and instead just use an external mature platform. Instead, we can put more focus on the client-side application. With a more engaging user experience. And where we can do things our way, using our favorite technology. All of that sounds nice, but what if we’re requested to migrate a well established, monolithic system into the new and fancy headless stack? Where do you start? What about missing features? How to maintain gained SEO? What are the additional benefits? In this talk, I would like to try to tackle those questions. Based on the story of our project which transferred a high load CMS eCommerce system (Magento 1) to an into headless Shopify with Gatsby front. With hundreds of products, while keeping the site URL structure the same – for SEO. Dealing with Shopify’s missing features, which not always could be resolved with the common "there’s an app for that" solution.