The event-driven architecture paradigm shift leads to clarity and inspiration, and designing systems for payment processing at scale using this approach is crucial. Event-driven programming models have evolved over the years, from distributed object (RPC sync), service-oriented architecture (SOA), enterprise service bus (ESB), to reactive programming and microservices. The event-streaming platform provides a data platform that behaves accordingly, with data models developed in relation to use cases. Stream processors are used for constructing flows from other streams, enabling logic execution or splitting, merging, and maintaining materialized views. Persistence is significantly different in the streaming model, where events are front and center, and state is maintained by event processors using incoming streams. The event streaming platform provides elasticity, correctness guarantees, and solves conventional microservice concerns. Event sourcing is another mechanism that can use a specific framework or be built into various implementations, but requires dedicated process control to ensure point-in-time or snapshot state is correctly rebuilt. Stream processor stateful operations like join, enrich, window, aggregate, etc., are stored at the partition level, and all of these elements compound upon each other with the repeated notion that events capture facts, streams capture behavior, and a series of related events tells a story. The event streaming platform replaces microservice frameworks and solves first-class concerns like event routing, service discovery, persistence, and elasticity, enabling continuous extension of functionality and evolutionary change.