Continuous Integration/Deployment (CI/CD) pipelines are critical for integrating developer changes and maintaining high-quality software deployments. The increasing frequency of commits and deployments places significant demands on CI/CD systems, requiring improved speed and efficiency. While numerous tools and techniques have been proposed to increase the velocity of CI/CD pipelines, there is a notable gap in architectural guidance for developers on key design decisions and best practices. To address this, we conducted a grey literature review using Straussian Grounded Theory to develop a UML-based model to guide software architects and developers in their decision-making. Our research focuses on identifying architectural design decisions (ADDs) and best practices as decision options that improve the speed and efficiency of CI/CD pipelines. The study analyses 38 sources, building a formal model comprising 6 ADDs and 30 best practices. This work contributes a structured, architecturally guided approach to optimizing CI/CD systems.