Persistent Systems MERN Stack Mid

Controlled vs uncontrolled inputs in React?

Controlled: value + onChange from state (easy validation). Uncontrolled: ref reads DOM. ShopNest checkout form is controlled so we disable Pay until fields are valid.

Persistent Systems rounds often probe: Product engineering.

Themes commonly reported in public MNC interview experiences (AmbitionBox / LinkedIn / Glassdoor-style). Practice aloud; keep answers this short in the real round.

More Persistent Systems MERN Stack questions

What is the Virtual DOM in React?
Explain useState and useEffect with a real example.
What is middleware in Express?
Explain the Node.js event loop simply.
MongoDB vs SQL — when do you pick each?
How do you secure a MERN API?

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