This talk was presented at code.talks 2022 in Hamburg. Learn more about code.talks at: https://codetalks.de/ Download Slides at: https://codetalks.de/speakers#talk-1128?event=7 Video recording on Youtube: https://www.youtube.com/watch?v=GC-hKOvQBus In this session, we will provide an introduction to REASON, also known as ReasonML. At SAP, we use REASON to build our Master Data Integration (MDI) Service as part of SAPs Business Technology Platform. MDI is a highly scalable, distributed, multi-tenant system powered by functional programming. REASON, is our language of choice for MDI: It lets you write simple, fast, and type save code. With REASON, you rarely have to annotate types, but everything gets checked for you through REASON’s type inference system, reducing bugs and increasing code maintainability. REASON translates to OCaml or JavaScript, providing access to both worlds and enabling it to run on NodeJS. During the session, we will highlight the advantages of the syntax compared to Java and introduce you to the beauty of immutability, tail recursion and other relevant concepts. Our session targets programmers who are not yet familiar with functional programming, as well as functional programmers who want to learn more about REASON.