Developers around the world are moving to rapidly adopt Domain-Driven Design (DDD), and in greater numbers than ever before. That's because DDD delivers powerful results in practice. At the same time, Reactive software development is becoming essential to implementing responsive, resilient, elastic, and message-driven solutions, including event streams of fast data. This world of distribution, concurrency, latency, and the uncertainty of time-critical results, must be tackled along with the complex business challenges. This talk gives practical guidance on using DDD to model business-driven solutions that result in software that is fluent, type-safe, and with core Reactive properties. Specific attention is given to moving legacy systems that have deep debt to ones that have clear boundaries, deliver explicit and fluent business models, and exploit modern hardware and software architectures.