As the system architecture become increasingly dependant on external and internal APIs, data transformation can quickly become a nightmare. Transforming the data for one system to the another becomes complex and hard to maintain. This talk dives into the challenges I faced managing over 100+ API integrations, where traditional JavaScript approaches led to a tangled web of complex, error-prone code. I'll explore what were the challenges of such API integrations at scale and how the development of a custom domain-specific language (DSL) for JSON transformation solved those challenges. How this solution dramatically simplified our codebase, improved maintainability, and boosted performance. As the JSON templating language I created is Open Source, anyone can use or fork this language to solve their own data transformation challenges. After this talk, you'll leave with more confidence with the knowledge of a new approach to bring order to API integration chaos