Developed Prometheus-based metrics for conference registrants in the cloudnativedaysjp/dreamkast repository, enabling real-time monitoring of online and offline attendee counts to support improved capacity planning. Leveraged Ruby for backend development, integrating Prometheus gauges with the StatsOfRegistrant data source to provide accurate, up-to-date metrics. Refactored existing code by removing dead code from DreamkastExporter related to registrant metrics, which reduced technical debt and enhanced maintainability. Focused on metrics and monitoring, the work improved observability for conference operations and facilitated data-driven decision making. The changes were delivered through targeted feature development and code cleanup, emphasizing reliability and clarity in the codebase.