MongoDB Senior Software Engineer Interview Experience — Six Rounds Including a Code Review, Director Wanted More Seniority

For DSA I just did LeetCode, steadily, over the past few months. For system design (both low-level and high-level) I went with an online design course without thinking twice, and I also watched a couple of YouTube channels on the topic.

Here is how the loop went:

1. Technical Screening: I had to build a rate limiter that lets through n requests within the last k seconds. We talked through the API and the code, and also the locking problems we would have to deal with in production. The follow-up was to make the limiter work per key.

2. Coding: It opened with a leadership question about ownership. Then came a variation on a time-based key-value store. I talked through two designs, one that burns memory but answers in constant time and another that uses less memory but is slower. I laid out the interface and coded one of the two.

3. System Design: The task was a small metrics monitoring system with only a few instances. I defined the metrics, the APIs and the overall approach, but the focus was really on monitoring MongoDB instances running on AWS or some other cloud. Later we drifted into scaling it and how Flink and Kafka could be combined to get close to real time. Notifications and alerting were declared out of scope. It finished with another leadership follow-up.

4. Code Review: Another leadership question first, this one about working in a team. Then I got a small coding project and had to review it, finding gaps, implementation problems and API issues. I managed to cover failure handling, badly designed APIs and ownership problems, and I also spotted a function that was implemented wrongly.

After that I got a green flag and moved on to the hiring manager and director rounds:

5. HM: We started with a project I had led on my current team. It was a general leadership and behavioral conversation, and I mostly stuck to the STAR method.

6. Director: Same kind of framework as the HM round, with a somewhat deeper dive into my previous projects.

Overall the interviewers were very accommodating and I enjoyed the whole loop. The director felt that for this particular opening they needed someone more senior than me. I'm still waiting to see whether another team opens up a spot for me. Fingers crossed.