This Master’s Thesis presents the design and implementation of a middleware solution for real-time monitoring of private APIs within Techtiva’s software ecosystem. The project addresses the need for greater visibility, reliability, and maintainability of internal APIs by developing a modular middleware in ASP.NET Core, integrated with InfluxDB for time-series data storage and Grafana for interactive visualisation. The system captures and analyses key metrics such as response times, error rates, and usage patterns, enabling proactive detection of issues and supporting data-driven decision-making. Containerisation with Docker ensures easy deployment and scalability across environments. The solution has demonstrated its effectiveness in improving API observability, supporting fast troubleshooting, and laying a robust foundation for future enhancements and advanced analytics.