Modern astronomical web platforms increasingly integrate interactive data exploration, authenticated data access, and online analysis services. As these capabilities expand, usability, accessibility, and security become fundamental design requirements. We present the Cherenkov Telescope Array Observatory (CTAO) Science Data Challenge (SDC) Portal as a case study of how these complementary requirements can be addressed within a modern, open-source astronomical web platform.

The portal couples a React front end with a FastAPI microservice architecture and exposes observation metadata through International Virtual Observatory Alliance (IVOA) standards, including TAP/ADQL and ObsCore. These community standards make Cherenkov data accessible to astronomers beyond the high-energy community while promoting FAIR access to astronomical data through open interfaces and an open-source implementation.

Usability is supported through source-name resolution, coordinate and time conversions, interactive visualisations, reusable data baskets, and submission of selected observations as preview jobs. Accessibility is improved through colour-blind-safe visualisations and CTAO usability guidelines.

The platform follows a service-oriented architecture separating authentication, application logic, and data download. Authentication and authorization are handled through OpenID Connect. A dedicated download service resolves logical file names to distributed storage endpoints and performs OAuth 2.0 Token Exchange for direct file downloads. Persistent application data are associated only with pseudonymous user identifiers, while personal profile information remains confined to temporary session state. The platform is deployed using containers, Helm, and Kubernetes, supported by continuous integration, automated code quality checks, and Grafana observability. Together, these engineering practices improve software quality and maintainability, while ongoing cybersecurity hardening prepares the platform for future CTAO operations.