Full-stack production yield reporting and drill-down tool built solo for the QA team at Delta Electronics Thailand. Aggregates station-level pass/fail data across factories and models, with drill-down to individual repair records and Excel export. Fixed an N+1 query, parallelized cross-schema data fetching, added row virtualization for 10,000+ row tables, and traced a session-hydration race condition that had been silently breaking deep links app-wide. Deployed in Thailand with rollout planned for Taiwan.