Micro-SaaS is an emerging trend in the software industry, supported by an ongoing fragmentation of the software landscape and increased readiness of enterprises to purchase software as a service. Micro-SaaS offerings are coming from two angles: First, established software vendors who have mastered scalable distributed architectures and are now turning microservices and microfrontends into standalone offerings. Second, startups or individual developers with a highly specific business model centered around a single capability. In this talk, participants will learn about architectural and engineering patterns that are needed to turn microservices, APIs and microfrontends into full-fledged commercial products: Self-service onboarding, identity/access management, consumption metering, tenant isolation, invoicing and billing. All of this with scalability and evolvability in mind which are essential for successful SaaS.