Platform-as-a-Service is a cloud-based approach that provides enterprises with all the functionalities for developing, deploying, and administering services, without the burden of installing, configuring, and managing the underlying middleware, operating system, and hardware. In this context, scalability becomes a fundamental requirement, and appropriate solutions need to be studied and evaluated. In this paper, we present different scalability patterns for a Platform-as-a-Service infrastructure and a two-level approach to performance monitoring allowing automatic scalability management. We also provide a performance evaluation of the scalability patterns on a Service-Oriented Architecture (SOA) PaaS, which considers the impact on performance of SOA security standards.