Promise = one result. Observable = stream (can emit many, cancel with unsubscribe). HttpClient returns Observables. ShopNest search uses debounce on an Observable so we do not hit API every keystroke.
Tech Mahindra rounds often probe: Full-stack JS/.NET.
Themes commonly reported in public MNC interview experiences (AmbitionBox / LinkedIn / Glassdoor-style). Practice aloud; keep answers this short in the real round.