Comprehensive guide to IndexedDB for full‑stack devs: why client‑side storage matters for PWAs and offline‑first UX; how its NoSQL key‑value model, transactions, async API, indexes and IDBKeyRange enable fast queries on large structured data; practical steps to open DBs, define object stores, do CRUD and queries; pitfalls like quotas, serialization, and error handling; includes a fitness app offline‑sync example.
