Zscaler Interview Experience For Java/API Developer Intership (Off-Campus)

Hello everyone, I am from ECE Branch (2020-2024 batch).

I have been selected for Zscaler Java Developer Role (Intern + FTE) & here is my journey of the same. I hope my experience would be helpful for you in your placement journey.

Rounds:

The selection procedure was overall divided into 4 rounds:

Round 1: OA Round

Zscaler during the time of OA opened 2 more roles other than the C Developer role.

These two roles were: Java/API Developer & UI/UX Developer.

One could apply for any one amongst the 3 available roles & I applied for the Java/API Developer role.

The OA contained 3 questions out of which I was able to solve 2.

The 3 questions were:

A design & OOPS based question where multiple classes & interfaces were given & the question asked to implement them.
Can make palindrome from substring. (Leetcode)
Given a town containing n houses & an integer array denoting infected houses. The question demanded to find the total number of distinct infection sequences possible.

I was selected for the further interview rounds.

Round 2: Technical Interview

It was the first technical round in the selection procedure. The interviewer was quiet friendly & he started with his introduction first, then he asked me to introduce myself.

He then directly jumped over DSA problems, but the problems he asked were very easy.

First, he asked me to get the middle node of a linked list using single traversal, then he discussed its time & space complexity.
The second question he asked me was Level Order traversal of a binary tree & then again, he asked about the time & space complexity of the problem.

After the DSA Questions, he asked me about my internship.

He asked me draw the structure of my internship project & what were my contributions in the project. I mentioned it with a great detail & the interviewer seemed satisfied with my response.

Then we moved to the core subjects.

At first, he asked me about the 7 layers of the OSI Model from Computer Networks.
From OS, he asked me about what different scheduling policies I know.
Then he asked me about what are semaphores.
Dining Philosopher Problem.
Finally, he asked me how deadlocks are handled in OS.

The interview lasted for about 50 minutes & it went pretty well. The interviewer also seemed satisfied with my responses.

After a few days, I received a mail regarding the 2nd interview round.

Round 3: Technical Interview

In the second round, the interviewer asked me to introduce myself.

Majority of the questions in this round were from OOPS & core Java.

At first, he asked me about any new features of Java 8 as compared to the older versions of Java. I was not able to recall the features of Java 8 at that time, but since Java 21 was newly released by that time, I knew some features of Java 21 & so I mentioned some of the new features of Java 21 that I knew & the interviewer as like OK with that stuff.
Then he asked me about different memory locations in Java & then later asked me where variables & objects are stored in java.
He also asked me to explain the meaning of: ‘public static void main(String[] args)’ in java & later added a scenario question that: what if my project contains only a single file (i.e. no possibility of calling the current file from any other file), in this case can the ‘public’ keyword be removed?
He then asked me what all stuff I know in the Collections Framework & asked me about the working & time complexity of HashMap & TreeMap in Java.

Then he moved towards OOPS.

I was told to describe the 4 pillars of OOPS in detail.

Later, we moved to the project section.

Here, the interviewer asked me about the E-Commerce project that I had created.

At the end, he asked me only one DSA question.

He addressed the question considering the scenario: if I had an array of integers denoting the salary of various employees. He asked me how can I get the 3rd largest salary from the array. I initially told him the brute force method by sorting the array & then we can get the 3rd largest salary. But he insisted on getting the result without sorting the array as if there were millions of entries in the array, then nLog(n) would be tremendous.
I remembered the Quick Select algorithm (to get the Kth smallest element in O(n) time). I told him the approach & the interviewer was satisfied with my approach.

The round was like a rapid fire round & lasted for about 50-55 minutes. The interview went pretty well & I was waiting for the results.

In about 2-3 hours after the 2nd round, I got the mail for the 3rd round.

Round 4: Technical + Managerial Interview

The 3rd round was technical, plus managerial questions were also asked in the end.

The interview began with my introduction.

At first, he asked me if I had worked with any containerized environment in Java. I hadn’t worked with any of that stuff & therefore said no that I haven’t worked with that stuff.

The interviewer than moved to the DSA section, but asked pretty easy questions:

How to create Stack using Queue.
Given a string, get all possible permutations of the string.

We then moved to the managerial questions, where he asked me some scenario based questions like:

What kind of person you are? Do you like to work individually or with a team?
How do you manage your projects if the deadline is very near?
Let’s say you have finished a project & submitted it to you manager prior to the deadline. Your manager hasn’t seen your work yet but is insisting you to change your approach for the project. What would you in that case?
At last, he asked me what would you do if we provide you the offer?

The interview ended up pretty well with these questions.

Finally, the results were declared & I was selected & given the offer of 6 months intern + FTE for the Java/API Developer role.

Preparation:

Coding in Java was not new to me. I began coding in Java since 2nd Semester & hence was quite comfortable with it.

Moreover, it is important to have a good grasp over the Data Structures & I really find it necessary to make a note of all the important topics covered as the final notebook makes it much easier to revise & go through all the stuff quickly.

Also, from interview point of view, it is really necessary to have a strong knowledge of all the CS Fundamentals (OS, OOPS, DBMS, CN).

Additionally, I would also like to mention some important sources through which I learnt & which I feel might really be useful to you as well.

1. Java

Oracle Certified Professional Java SE 11 Programmer I Study Guide
Telusko Channel (Youtube)
Java Collections Framework: GFG, GFG

2. DSA

Many ‘Bhaiya/Didi’ channels (not possible to mention all of them)
Babbar & Striver Sheets
Leetcode
GFG Practice

3. Core Subjects

OS
OOPS
DBMS
CN
OOPS & DBMS taught in the course are really more than sufficient to answer any question asked during the interview.
Gate Smashers videos are also very helpful while learning these topics.
If you still want to dive deep into these topics, then go through GFG, JavaTPoint, etc (and a lot more websites) to have a good command over these topics.

4. Puzzles

Although, I wasn’t asked any puzzle during the interview, but it is good to prepare them beforehand.
Top 20 GFG Puzzles
Top 100 GFG Puzzles (if time permits)