I went through an on-campus interview process for a Software Engineer role at Zenon.

Round 1: Objective Exam

The first round was an offline objective exam conducted in my college's lecture hall. Out of 140 students, I was among the 20 shortlisted for the next stage. The exam comprised three sections: Maths/Aptitude, DBMS/OS, and SQL queries. It required a strong grasp of core computer science subjects, and there was a 25% negative marking.

Round 2: Technical Interview 1

In this round, the discussion primarily revolved around Java architecture, SQL queries, and an optimization problem. The interviewer started by asking me to introduce myself. Then, we delved into Java-specific questions such as: "What is bytecode in Java and its use?", "What is JVM?", "Can we install multiple JVMs on one system, and what would be the benefit?", and "What are Iterators in Java?".

A significant part of the round was a problem where I had to process words from a file: store words less than 5 characters long directly into a new file, and for words greater than 5 characters, remove all vowels before storing them. I was also asked to optimize these operations for space and time. Finally, I was given a SQL query to "Display the name of the department and the count of students in each department from the 'department' and 'student' tables." After this round, 10 students, including myself, were shortlisted.

Round 3: Technical Interview 2 (System Design)

This round focused on system design. After a brief introduction, the interviewer asked me to design a food delivery service, similar to Zomato, covering all required entities, their relationships, and associated operations. I had to explain my design approach and thoughts.

The second system design question involved preventing duplicate requests at the server side when a client repeatedly clicks a submit button on a web form. The third question was related to database table design: given that a student is associated with a department and can take multiple courses, I had to explain how many tables would be needed to organize this data effectively. I also faced a SQL query related to this configuration, though I don't recall the exact query.

Round 4: Technical Interview 3 (UI Design, OOPs, DSA)

This round again began with my introduction. Since my resume mentioned React.js, I was given a UI design problem: organize and maintain transitions between pages in a React.js application. This involved a login page, a home page with two links, and each link leads to a separate page. I explained my approach using local storage for login credentials, React Router for navigation, and hooks to manage props.

Next, a DSA question involved converting a number from 1-1000 into its English word format (e.g., 145 to "One Hundred Forty Five"). Another data structure question presented a network of friends (like Facebook connections) with timestamps. I had to identify the appropriate data structure and approach to answer queries such as "tell the time when F2 connected to F4."

The interviewer also covered OOPs concepts, asking about the "Difference between Method Overloading and Method Overriding," "What is Inheritance?", and an "Output prediction" problem involving multilevel inheritance. The round concluded with another SQL query: "Find the topper student name and his department name from each department in a university database," given 'Student' (id, name, dept_id, score) and 'Department' (dept_id, dept_name) tables. Only 3 students remained after this round.

Round 5: HR Interview

The final round was with HR. The questions were primarily behavioral: "Tell me about yourself," "From which city do you belong?", and "What are your tech interests?". The interviewer also touched upon OOPs, asking about the "Difference between Aggregation and Composition," and SQL, inquiring about "Joins and types of joins" and "Cartesian product and a real-world example."

Ultimately, two students, including myself, were selected.