StockVault.

Built a full-stack equity-research platform that scores 1,700+ Indian stocks 0–100 through a deterministic, four-guardrail Valuations Engine — explaining every verdict in plain English instead of acting as a black box. Architected a provider-agnostic data layer behind a single repository interface with runtime-swappable backends (committed JSON snapshot, PostgreSQL, live microservice, mock), enabling zero-infrastructure local runs and secret-free CI builds. Engineered a 'cached page, live price' pattern — ISR/CDN HTML for fast LCP with a request-coalesced quote proxy (Python · FastAPI · yfinance) delivering a live 30s price tick. Weekly data refresh runs on GitHub Actions, with property-based tests (fast-check) guarding the engine.