This research aims to develop a web-based Hospital Information System (HIS) for the outpatient department to replace the legacy desktop system, which has accessibility limitations from multiple service points. A key highlight of this study is the development of a system focused on centralized, real-time workflow integration utilizing a three-tier architecture. The system covers seven main modules: 1) Doctor Screen, 2) Nurse Counter, 3) Patient Screening (PTScreen), 4) Treatment, 5) Medical History, 6) Doctor Summary, and 7) Patient Profile.
      The system was developed using React.js and Node.js in conjunction with a MySQL database. The system's performance evaluation was conducted through test cases. The results revealed that the system achieved 100% functional accuracy across all test cases. This demonstrates that the system can accurately retrieve and display medical history data from the existing HIS via an API in real time. Consequently, the system helps reduce data entry redundancy for healthcare personnel and can be practically implemented to tangibly elevate service efficiency in the outpatient department.