Node is single-threaded for JS but non-blocking for I/O. While waiting on Mongo/HTTP, it serves other requests. ShopNest API can handle many checkouts without one slow DB call freezing everything.
Siemens rounds often probe: Industrial software.
Themes commonly reported in public MNC interview experiences (AmbitionBox / LinkedIn / Glassdoor-style). Practice aloud; keep answers this short in the real round.