Ecom Express Software Development Engineer II Interview Questions and Answers

Round duration - 95 minutes
Round difficulty - Medium

The 1st round was online coding + MCQ round. It had 3 sections in total to be solved in 95 mins.
Next comes the technical interview. 
The technical interview lasted for about 45 minutes. It started with a basic introduction. Then, she framed some questions from my resume and projects which I have mentioned. Questions were mainly from Data structure, OS, DBMS, SQL. She told me to rate my data structure skill on a scale of 1 to 5.
My interview was at 10:30 am and the interviewer was really nice. She was helping me wherever I was getting stuck.

Q1. 
Fourth Largest Element in the Array
Given an array consisting of integers, your task is to determine the fourth largest element in the array. If the array does not contain at least four distinct elements,...read more
Ans. 
Find the fourth largest element in an array, return -2147483648 if not enough distinct elements.
• Sort the array in descending order

• Return the fourth element if it exists, else return -2147483648
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Round duration - 45 minutes
Round difficulty - Medium

The technical interview lasted for about 45 minutes. It started with a basic introduction. Then, she framed some questions from my resume and projects which I have mentioned. Questions were mainly from Data structure, OS, DBMS, SQL. She told me to rate my data structure skill on a scale of 1 to 5.

Q1. 
Sort 0s, 1s, and 2s Problem Statement
You are provided with an integer array/list ARR of size 'N' which consists solely of 0s, 1s, and 2s. Your task is to write a solution to sort this array/list.
Input:
...read more
Ans. 
Sort an array of 0s, 1s, and 2s in linear time with a single scan approach.
• Use three pointers to keep track of the positions of 0s, 1s, and 2s in the array.

• Iterate through the array once and swap elements based on their values and the pointers.

• After the single scan, the array will be sorted in place with 0s, 1s, and 2s in order.
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Q2. 
Remove Duplicates Problem Statement
You are given an array of integers. The task is to remove all duplicate elements and return the array while maintaining the order in which the elements were provided.
...read more
Ans. 
Remove duplicates from an array while maintaining order.
• Use a set to keep track of unique elements.

• Iterate through the array and add elements to the set if not already present.

• Convert the set back to an array to maintain order.
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Q3. Can you describe all the joins in SQL and illustrate them with a Venn diagram?
Ans. 
SQL joins are used to combine rows from two or more tables based on a related column between them.
• Inner Join: Returns rows when there is at least one match in both tables.

• Left Join: Returns all rows from the left table and the matched rows from the right table.

• Right Join: Returns all rows from the right table and the matched rows from the left table.

• Full Outer Join: Returns rows when there is a match in one of the tabl...read more
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Q4. 
Binary Tree Node Presence Problem
Determine if a node with a given integer value X exists in a specified binary tree.
Input:
The first line of each test case contains the binary tree nodes in level orde...read more
Ans. 
Check if a node with a given value exists in a binary tree.
• Traverse the binary tree using depth-first search (DFS) or breadth-first search (BFS) to search for the node with the given value.

• Use a recursive or iterative approach to implement the search algorithm.

• Return 'true' if the node with the given value is found, otherwise return 'false'.
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Q5. 
Shortest Path in an Unweighted Graph
The city of Ninjaland is represented as an unweighted graph with houses and roads. There are 'N' houses numbered 1 to 'N', connected by 'M' bidirectional roads. A road...read more
Ans. 
Find the shortest path in an unweighted graph from house 'S' to house 'T'.
• Use Breadth First Search (BFS) algorithm to find the shortest path in an unweighted graph.

• Create a queue to store the current house and its neighbors, and a visited set to keep track of visited houses.

• Start BFS from house 'S' and stop when reaching house 'T'.

• Return the path from 'S' to 'T' once 'T' is reached.

• If multiple shortest paths exist, ret...read more
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Q1. CODING ROUND - KTH LARGETS NO.
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Q2. EXPLAIN CICD PIPELINE
Ans. 
CI/CD pipeline automates software development processes, enabling continuous integration and delivery for faster, reliable releases.
• Continuous Integration (CI) involves automatically testing and merging code changes into a shared repository.

• Continuous Delivery (CD) ensures that code changes are automatically prepared for release to production.

• Tools like Jenkins, GitLab CI, and CircleCI are commonly used to implement CI...read more
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Q1. Csharp basics and a coding questing was given to implement
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Q2. .net and angular basics questions
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Q1. Asked deeply about my resume and technologies
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Q2. Coding question to sort a given array using DSA
Ans. 
Sorting an array of strings can be achieved using various algorithms like Quick Sort, Merge Sort, or built-in functions.
• Use built-in sort: In Python, use sorted(array) or array.sort(). Example: sorted(['banana', 'apple', 'cherry']) returns ['apple', 'banana', 'cherry'].

• Implement Quick Sort: A divide-and-conquer algorithm that sorts by selecting a 'pivot' and partitioning the array. Example: ['banana', 'apple', 'cherry'...read more
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Asked about most of the core java questions and design pattern and SOLID principles

Q1. Design rate limiter
Ans. 
A rate limiter controls the number of requests a user can make in a given time frame to prevent abuse.
• Use a token bucket algorithm to allow bursts of traffic while enforcing a steady rate.

• Implement a sliding window mechanism to track requests over time, e.g., allowing 100 requests per minute.

• Consider using Redis or in-memory data structures for distributed systems to maintain state.

• Provide feedback to users when they e...read more
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Q1. 1) OOPS 2) SOLID 3) Design Patterns 4) SQL Concepts
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Q2. LINQ joins on 2 tables
Ans. 
LINQ joins on 2 tables allow for combining data from both tables based on a common key.
• Use the 'join' keyword in LINQ to join two tables based on a common key

• Specify the key to join on using 'equals' keyword

• Select the desired columns from both tables in the result
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Q3. Example of Open close principle
Ans. 
Open close principle states that a class should be open for extension but closed for modification.
• Classes should be open for extension through inheritance or implementing interfaces

• Classes should be closed for modification to avoid breaking existing code

• Example: Using abstract classes or interfaces to define behavior and allowing subclasses to implement specific functionality
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It was a normal aptitude test with mathematical questions.

It was a techno-coding test where I had to code while sharing my screen on a live conversation with the interviewer.

Q1. I was primarily asked about managerial questions on adaptability to new technology and creativity if existing solutions don't work.
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Q2. In a situation where your team is not getting a proper result with existing approach your team uses, how would you try to fix it?
Ans. 
I would analyze the current approach, identify the root cause of the issue, brainstorm alternative solutions, and collaborate with the team to implement and test them.
• Analyze the current approach to identify weaknesses

• Brainstorm alternative solutions with the team

• Implement and test the new solutions

• Regularly communicate and collaborate with team members
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Round duration - 90 minutes
Round difficulty - Medium

This was a Data Structures round. Both questions were answered in optimal time complexity with clean code. Every other question was answered to the best of my knowledge

Q1. 
Rotting Oranges Problem Statement
You are given an undirected and disconnected graph G(V, E) with V vertices numbered from 0 to V-1 and E edges. Your task is to perform a BFS traversal starting from the 0...read more
Ans. 
Perform BFS traversal on an undirected and disconnected graph starting from vertex 0.
• Implement BFS traversal algorithm starting from vertex 0

• Use a queue to keep track of visited nodes and their neighbors

• Print the traversal order in sorted order for each node's connected nodes
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Q2. 
Smallest Integer Not Representable as Subset Sum
Given a non-decreasing sorted array ARR of N positive numbers, determine the smallest positive integer that cannot be expressed as the sum of elements from...read more
Ans. 
Find the smallest positive integer that cannot be expressed as the sum of elements from any proper subset of a non-decreasing sorted array of positive numbers.
• Start with the smallest possible sum that can be represented, which is 1.

• Iterate through the array and update the smallest sum that cannot be represented.

• Return the final smallest sum that cannot be represented.
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Q3. 
BFS Traversal in a Graph
Given an undirected and disconnected graph G(V, E) where V vertices are numbered from 0 to V-1, and E represents edges, your task is to output the BFS traversal starting from the ...read more
Ans. 
BFS traversal of an undirected and disconnected graph starting from vertex 0.
• Implement BFS algorithm to traverse the graph starting from vertex 0.

• Use a queue to keep track of visited nodes and their neighbors.

• Ensure to visit all connected components of the graph.

• Print the BFS traversal sequence for each test case in a separate line.

• Handle cases where not all vertices are reachable from vertex 0.
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Round duration - 100 minutes
Round difficulty - Easy

Mostly technical and System Design questions were asked.

Q1. Design an LRU (Least Recently Used) cache.
Ans. 
Design an LRU cache to store least recently used items efficiently.
• Use a combination of a doubly linked list and a hashmap to store and retrieve items in O(1) time complexity.

• When an item is accessed, move it to the front of the linked list to mark it as the most recently used.

• If the cache is full, remove the least recently used item from the end of the linked list and the hashmap.
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