← Back to Directory

MongoDB interview notes, page 1 of 2

Large Enterprises

Screna has 19 MongoDB interview write-ups. The most reported round is the technical phone screen (9).

19 interview notes · updated Jul 2026

MongoDB·Software Engineer·Technical Phone Screen

Apr 2026
MongoDB engineering manager interview with a code review exercise. They handed me a TypeScript React Tic-tac-toe implementation and asked me to tear it apart. Not what I expected going in.
  • Review this React and TypeScript Tic-tac-toe implementation and suggest improvements.

“Spent the first couple minutes just reading through it quietly which felt awkward but I needed to actually understand the code before saying anything.”

View Post

MongoDB·Software Engineer·Technical Phone Screen

Apr 2026
Short technical screen for a software engineer role at MongoDB. Just one question but it was open-ended enough to go a lot of directions depending on what you've actually built with.
  • Name three Python frameworks you're most familiar with and explain when and how you use each one.

“Went with Django, FastAPI, and Celery.”

View Post

MongoDB·Software Engineer·Onsite - Behavioral / Leadership

Apr 2026
MongoDB software engineer interview that centered almost entirely on a deep behavioral dive. Three main threads: career narrative, a hard technical project, and a failure story. Felt more like a senior engineering values screen than a traditional technical round.
  • Walk me through your background: key roles, domains you've worked in, and your most relevant accomplishments for this position.
  • Describe your most challenging project in depth: what problem were you solving, what was your scope, and what constraints made it hard?
  • What alternatives did you consider for that project, and what trade-offs pushed you toward the approach you ultimately chose?
  • Take me through the implementation: architecture, key components, data flows, and technology choices.
  • How did you validate your technical decisions, what risks did you mitigate, and what metrics did you track to measure success?
  • What would you do differently on that project if you were starting over today?
  • Tell me about a meaningful failure: what happened, what was your role in it, what was the root cause, and how did it change how you work?

“I'd prepped a version of this but still rambled a bit connecting my earlier work to the current role.”

View Post

MongoDB·Software Engineer·Technical Phone Screen

May 2026
Got a coding question from MongoDB that looked straightforward until I actually had to think about the search space. Binary search on the answer, not the index, which is a pattern I keep forgetting exists.
  • Given an integer array and an integer k, split the array into k non-empty contiguous subarrays such that the largest subarray sum is as small as possible. Return that minimum possible largest sum.

“My first instinct was DP and I started going down that path before catching myself.”

View Post

MongoDB·Software Engineer·Recruiter / HR Screen

May 2026
Prepped for a MongoDB interview and got hit with the classic 'why us' question. Not much to report beyond that one prompt, but it's the kind of thing that trips people up if they haven't actually thought about it.
  • Why do you want to work at MongoDB specifically? What draws you to the company's mission, products, or culture, and how does it connect to your background?

“I blanked a little because my first instinct was to say something about liking databases, which, yeah, not exactly a differentiator.”

View Post

MongoDB·Software Engineer·Recruiter / HR Screen

May 2026
Screened for a role at MongoDB where the main ask was a structured self-introduction. Pretty low-key as far as interviews go, basically just a chance for them to hear how you present yourself before anything technical.
  • Give a 2-3 minute introduction of yourself covering your background, current role, key projects, and what you're looking for next.

“I always fumble the ending on these.”

View Post

MongoDB·Software Engineer·Technical Phone Screen

May 2026
Got a coding question at MongoDB for a software engineer role that was deceptively simple on the surface but had a few edge cases worth thinking through carefully.
  • Implement a 'union iterator' that takes two sorted, duplicate-free iterators as input and produces a single sorted output with no duplicates, merging values that appear in both into just one.

“My first instinct was to just dump everything into a set and sort it, which works but completely misses the point.”

View Post

MongoDB·Software Engineer·Onsite - System Design / Architecture

May 2026
MongoDB system design round, clearly aimed at senior/staff level candidates. The whole thing was one long deep dive into network server performance, and it went places I wasn't fully prepared for.
  • A concurrent network server is struggling under heavy load. Walk through how you'd diagnose the performance problem and fix it, covering everything from connection lifecycle and accept/handshake costs to event loop dispatch, blocking vs non-blocking I/O, multiplexing primitives like select/poll/epoll/kqueue/io_uring, epoll level-triggered vs edge-triggered modes, io_uring's queue model vs epoll's readiness model, threading architectures, and where backpressure builds up.

“This was basically the whole interview compressed into one question.”

View Post

MongoDB·Technical Program Manager·Recruiter / HR Screen

May 2026
Interviewed for a TPM role at MongoDB, and from what I can tell it was a pretty standard screen. Only one question surfaced from the content so hard to say much about the full loop.
  • Why do you want to work at MongoDB specifically?

“Pretty expected question but I still fumbled it a bit.”

View Post

MongoDB·Machine Learning Engineer·Technical Phone Screen

May 2026
Did a technical round for an MLE role at MongoDB and got completely stuck on a dynamic programming problem. The interviewer was patient and walked me through it with hints, but when you don't have the core idea, hints only go so far.
  • Given two integer arrays of equal length, assign elements from one array to the other (as a permutation) to minimize the total XOR sum across all pairs.

“Blanked completely.”

View Post