Ola | SDE2 | Feb 2021 | Pune | Offer

Interviews Breakdown

I was initially contacted by a recruiter from Ola who was incredibly flexible with scheduling all the interview rounds, providing excellent support throughout the process.

Problem Solving Round 1

This round consisted of two easy Data Structures questions, primarily related to arrays and strings. Unfortunately, since it was about a month ago, I cannot recall the exact problem statements, but they were comparable to LeetCode easy problems.

Problem Solving Round 2

This round, which was 15 days prior, was scheduled for one hour but concluded in about 40 minutes after I addressed both questions successfully.

• Question 1: Given an array, I had to determine if it could be sorted by reversing any single subarray within it. For example, in [1, 2, 3, 4, 8, 7, 6, 9], reversing the subarray from index 4 to 6 would result in a sorted array.
• Question 2: This was a variation of the Two Sum problem. I needed to find pairs of numbers in the array [1, 2, 3, 4, 8, 7, 6, 0] that sum up to 6. It was assumed that numbers were positive and distinct, with expected output like [[2,4], [6,0]].

System Design Round

This round took place three days before the offer. It began with a discussion about my current project, where I was asked to draw a block diagram of its various components. Following that, the main task was to design a seat booking system similar to BookMyShow.

• GetSeatsInfo: This involved designing how to fetch seat information, including grid details, screen layouts, seat categories, and color coding for the UI. I discussed storage mechanisms in the database and the structure of request/response payloads.
• BookSeats(User u1, array of SeatsNumbers, ScreenId, TheatreId): The core challenge here was managing concurrency and consistency issues during seat booking. This discussion went very smoothly, and it felt like a collaborative effort in building the solution.

Hiring Manager Round

The hiring manager round, held the day after the design round, lasted about 1 hour and 45 minutes and was the most intense. The questions were spontaneous, and the interviewer delved deeply into every detail I mentioned, thoroughly examining my resume.

• I was asked about the most challenging project I've worked on, including the specific challenges, how I overcame them, and the tech stack used.
• The interviewer inquired about the rationale behind choosing that particular tech stack and, hypothetically, if I were to rebuild the project from scratch, what new tech stack I'd select and why.
• Since I mentioned microservices, I had to justify that choice, describe how microservices would be implemented in my current project, and specify the tech stack for each.
• We discussed flaws in my current project and the problems with NoSQL databases that might lead one to switch to relational ones.
• A complex scenario involved designing an analytics approach for my project without using a relational DB. I proposed a data pipeline and was then asked to design its workings.
• Numerous questions followed on messaging systems (RabbitMQ, Kafka, their differences, components, necessity, and real-world use cases), Redis (what it is, if it can be used as a message queue), and caching concepts.
• My experience with application monitoring tools like Kibana and Grafana was explored, including their internal workings, how I would design such a system, and appropriate database choices (especially Cassandra for write-intensive scenarios).
• Integration of logging tools, container-specific details, and log pushing mechanisms to Kibana were also discussed.
• Fundamentals of load balancing, proxy vs. reverse proxy, ZooKeeper, and sharding (when and why it's needed) were covered.
• Finally, several behavioral questions were posed, such as conflicts with managers/peers and their resolution, best and poor performance feedback received and how I handled it, and my motivation for joining Ola.
• I also had the opportunity to ask questions at the end.