persistent systems | on-campus 2021 | online assessment questions | interview questions

I participated in the Persistent Systems on-campus drive in 2021, aiming for an entry-level position. The entire process consisted of multiple rounds, starting with an initial assessment and progressing through advanced coding, technical interviews, and a super achiever round, culminating in an HR assessment. I managed to clear all rounds, eventually securing the highest package offered.

The first hurdle, Round 0, involved 50 logical reasoning and English questions, where I solved approximately 40. This was followed by two very easy coding questions, both of which I successfully completed. Surprisingly, I wasn't interviewed in this technical round.

Following a strong performance, I was invited to the Advanced Coding Round OA which was designated for high-performers, targeting a 7.5 LPA package. This round featured two coding questions to be solved within 60 minutes. The first problem required converting one binary string to another by reversing substrings, with a constraint on increasing substring size; I solved this. The second problem, on finding the edge part of the maximum number of simple paths in an undirected graph, was more challenging, and I couldn't pass all test cases.

Next was a 90-minute Technical Interview. I was asked to code two problems: printing Pascal's Triangle and sorting an integer array by frequency, preserving the original order for elements with equal frequency. Both solutions were rigorously tested with multiple test cases, and I passed. The interview also included three SQL queries: creating a table, inserting data, and finding duplicates based on two columns, which I solved using GROUP BY and HAVING. Additionally, several CS fundamental questions were posed, covering topics like heaps, selection sort, pointers vs. references, disadvantages of the waterfall model, array declaration differences in certain languages, exceptions, and the distinction between exceptions and errors. I managed to answer most of these, though I missed the array declaration difference.

After successfully clearing the previous stages, I moved to the Super Achiever Round, aiming for a 9 LPA package. This began with a Coding Round of two problems in 60 minutes. The first problem was identical to the 'Number of Islands' problem on LeetCode, which I solved. The second problem was a variation of finding connected components in an undirected graph, and while not straightforward, I also managed to solve it.

The final Interview in the Super Achiever Round was managerial and focused on advanced topics, lasting 30 minutes. I was challenged with a system design-style question on finding word frequency in a huge text file, where a naive approach (chunks + hashmap) was explicitly deemed insufficient. I also solved a simple SQL self-join problem. The CS fundamentals portion delved into Python-specific concepts like context managers and GIL (which I couldn't answer), along with recursion (types, tail recursion optimization, and efficiency compared to loops), network architecture layers, reliable transmission, and functions of transport/network layers. Database questions included RDBMS indexes and their types (I missed the types). Since I mentioned ML on my resume, I was asked to explain the bias-variance tradeoff and normalization, both of which I answered.

Finally, the HR round was a 15-minute assessment of 50 objective, situational questions, which apparently everyone passes.

I am pleased to report that I successfully navigated all these rounds and received an offer with the highest package.