How do you digitally-enable disparate and disorganised data? We needed to create an API that could consume and output data that was not originally designed for the digital age. Our challenge was to transform this data into a beautiful, cohesive output for a major company in Switzerland. This is the story of our multi-year architecture journey, successfully integrating and managing large volumes of data from various APIs with different formats. In this case study I will discuss how we built a resilient and adaptable API that that handled real-life legacy data and presented a modern consistent interface. We will cover the importance of the DataMapper pattern in managing data transformation and integration, along with how our approach to serializing and versioning the API was crucial for maintaining functionality and relevance. By the end of this talk, you will be understand the challenges of dealing with a lot of different formats of data and understand how you can create a modern API from it.