E-Commerce Product Discovery at Scale
Frontend: React + TypeScript with faceted filtering (price, genre, condition, author). Debounced search, optimistic UI updates, client-side cart state via Context.
Backend: Express API with request validation (Joi). Parameterized queries prevent SQL injection. JWT auth with secure token handling.
Database: PostgreSQL with composite indexes on frequently-filtered columns. Proper schema normalization: books → editions → inventory → orders. Query optimization via EXPLAIN ANALYZE prevents N+1 problems.
Performance: Sub-200ms API response time for filtered product lists. Pagination implemented server-side with proper sorting at database level.
Key challenge solved: Making filter combinations work instantly by combining filters in single parameterized query rather than sequential requests.