MongoDB interview experience Real time questions & tips from candidates to crack your interview

SDE - Intern

MongoDB

1 rounds | 2 Coding problems

Anonymous

Fresher | Jul 2025

Rejected

Interview preparation journey

Application story

MongoDB visited our campus, and the CGPA criteria were high at around 8.5. I had a CGPA of 8.9, so I was eligible. The company directly shortlisted candidates for interviews based on their resumes.

Why selected/rejected for the role?

I got rejected because I panicked and fumbled on a relatively easy DSA problem. The interviewer gave hints to guide me toward a simpler approach, but I missed them due to a lack of focus.

Preparation

Duration: 6 months

Topics: Data Structures, OOPs, Time complexity, DBMS, Operating System, Dynamic Programming

Tip

Tip 1: Be consistent with DSA practice.
Tip 2: Try to solve questions on your own before looking at the solution.
Tip 3: Analyse the time and space complexity of your solution.

Application process

Where: Campus

Eligibility: 8.5 CGPA, (Stipend: 1L per month)

Resume tip

Tip 1: Keep your past experience and internships authentic.
Tip 2: Clearly define your project’s motivation and scope for improvement.

Interview rounds

Round

Easy

Online Coding Test

Duration60 minutes

Interview date31 Jul 2025

Coding problem2

The interview was conducted on the Karat platform. The interviewer introduced himself and then moved straight to the coding questions.

First, he showed me a code snippet and asked me to identify the error in it.
Second, he showed a problem along with the solution code and asked me to name the algorithm and describe its time complexity.
Third, he asked a DSA problem.

1. DSA

This was the code for the Dijkstra's algorithm the interviewer asked me to find the error in that. (Learn)
Quick sort code was shown and I was asked to tell the time complexity. (Learn)

Problem approach

In the code for Dijkstra's shown, the condition to change the distance of node was not correct.

2. Reverse Pairs

Hard

50m average time

90% success

0/120

Asked in companies

You are given an array/list say ‘ARR’ of size ‘N’. We call pair (i, j) a Reverse Pair when i < j and 'ARR[i]' > 2 * 'ARR[j]'.

Your task is to find the number of Reverse Pairs present in given 'ARR'.

For example :

For the array [50, 21, 9], if we follow 1-based indexing, the Reverse Pairs are (1, 2), (1, 3) and (2, 3). Thus, the total count i.e. the answer becomes 3.

Note :

A single index of the pair (i, j) can be used multiple times.

Problem approach

I applied the brute force
First, we will run a loop(say i) from 0 to N-1 to select the a[i].
As index j should be greater than index i, inside loop i, we will run another loop i.e. j from i+1 to N-1, and select the element a[j].
Inside this second loop, we will check if a[i] > 2*a[j] i.e. if a[i] and a[j] can be a pair. If they satisfy the condition, we will increase the count by 1.
Finally, we will return the count i.e. the number of such pairs.

Try solving now