NPCI Full Stack Engineer Interview Experience: core Java, OOP, and a React question

The interview began immediately with an introduction about me, then moved into core Java and OOP fundamentals. I was asked about inheritance and how I would implement it in a small Java program. I needed to explain the code clearly, including what it did and how its pieces worked together.

The discussion went deeper into Java-internals topics. I was asked about the diamond problem and how HashMap works under the hood. Near the end, it shifted toward the front end with a React question about form-validation implementation, which surprised me after such a Java-heavy conversation.

The atmosphere was easy and friendly. The interviewers were approachable and even joked while asking questions, so the detailed Java material did not feel adversarial. I did not receive an offer, but it felt like a straightforward, foundations-first screen.

Location: Hyderābād. Overall feedback: Positive. Offer status: No offer.