Due to the exponential growth of mobile banking and the increasing competition from the fintech world, in order to stay head, traditional banks are required to offer better services and dramatically reduce their development lifecycle. A key aspect here is played by APIs. In fact, having a scalable and performant cross-country cross-system internal API layer is the foundation for building better services, faster. During this talk we will explain how an API layer can be implemented, which can be used as a foundation for every service offered by the bank. We will cover multiple aspects such as core system offloading, event sourcing, caching and micro-services.