Top DoorDash Interview Questions for Software Engineers

Cracking the tech interview at DoorDash can be challenging. However, you can outperform the competition by thoroughly preparing for frequently asked DoorDash interview questions. One of the leading online food ordering and delivery platforms, DoorDash is constantly looking for software engineers.

Software engineers at DoorDash work on everything from backend systems, creating well-designed and thoughtful user interfaces to scaling products to automate human processes and make deliveries quick.

DoorDash technical interview questions form a crucial component of the interview loop for software engineers. DoorDash designs interview questions to effectively gauge your ability to perform in the specific role. You should be able to showcase expertise in data structures and algorithms to ace the DoorDash technical interview.  Your ability to effectively communicate and solve problems is vital.

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The DoorDash technical interview will be challenging. The interviewer will look for qualities that will work as an asset to the technical team and fulfill the company's business goals. So in this article, we’ll share a list of DoorDash interview questions that will help you boost your tech interview prep.

Here's what we'll cover:

• DoorDash Technical Interview Questions
• Tips for Answering DoorDash Technical Interview Questions
• DoorDash Case Interview Questions
• Non-Technical Interview Questions DoorDash
• FAQs on DoorDash Interview Questions

DoorDash Technical Interview Questions

Hiring managers at DoorDash tend to ask fewer behavioral and soft skills interview questions compared to other tech companies.

So you must have a firm grip over data structures and algorithms to ace DoorDash technical and coding interview questions.

DoorDash Coding Interview Questions

At DoorDash, you will get a take-home project as a part of the coding interview rounds. Here, the interviewer will ask you to add or change a feature within an already built application.

However, iOS coding interviews do not have any take-home projects. Instead, you will have to participate in a technical phone screen round and work with an iOS engineer in completing a partially finalized application.

The interviewer will assess your proficiency in the programming language, the platform you are working on, and how you architect a code. DoorDash asks mostly LeetCode questions in coding rounds focusing on strings, arrays, and edge cases.

Some common DoorDash Interview questions requiring coding are:

1. Write a program to complete the partially filled (9 x 9) Sudoku. (Answer)
2. For a given N number of elements, write a program for counting the number of triplets that have a sum less than the given value.
3. Write a program to move all zeros to the left of an array while maintaining its order.
4. You are given a 2D matrix with only 0 (representing water) and 1 (representing land) as entries. In the matrix, an island is formed by grouping all the adjacent 1's connected 4-directionally (horizontal and vertical). How would you find the maximum area of the island in the matrix? Assumption: All four edges of the grid are surrounded by water.
5. For a given array of integers, find the combination of three elements whose sum is equal to a given value X. Print the first combination that you get. If there is no such combination, then print -1.
6. Write a program to return the type of a triangle based on the length value of the three of a triangle. Assumption- test for the input data type is already in place. You get only numeric values.

Practice more coding interview questions and check their solutions on the Problems page to ace coding interviews.

DoorDash Interview Questions on Algorithms

If you are a software engineer, software developer, or engineering manager, you should be well-prepared for DoorDash interview questions on algorithms. For algorithms, you must be adept in the following:

• Graphs: Dijkstra's, BFS, DFS
• Tree traversals, including Preorder, Inorder, Postorder
• Linked lists
• Recursion: Divide and conquer base case and recursive (inductive) cases, tail recursion, dynamic programming solutions to recursive questions
• Search and sort: Quicksort, merge sort, heap sort, insertion, bubble, binary search

Here are some DoorDash interview questions and answers on algorithms for your practice:

1. What is the fastest searching algorithm?

Binary search is the fastest searching algorithm and is widely used for efficient searching. It has a time complexity of O (log n).

2. What do you understand about greedy algorithms?

Greedy algorithms work step-by-step. They always choose the steps that result in immediate profit/benefit. They choose the locally optimal solution. Greedy algorithms may not always provide the optimal global solution, as they don't consider the entire data. Examples are Knapsack, Dijkstra’s problem, Prim's, and Kruskal's.

3. What are the most widely used cryptographic algorithms?

The most widely used cryptographic algorithms are:

• IDEA
• Blowfish
• GOST
• CAST
• CMEA
• 3-way
• LOKI
• DES and Triple DES

4. What do you understand about the space complexity of the insertion sort algorithm?

Insertion sort is an in-place sorting method. It does not require any minimal or additional data storage. Only a single list element should be stored outside the starting data, resulting in a constant space complexity [O (1)].

Here are some more DoorDash algorithm interview questions:

1. Write an algorithm to find the largest subarray sum for a given array of integers.
2. Write an algorithm to insert a node in a Binary Search Tree.
3. For a given sorted array and a number N. How would you find the pair whose sum is closest to N?
4. How would you find the level of a node in a binary tree?
5. How will you count inversions in a sorted array?
6. Write an algorithm to reverse a linked list using recursion and iteration?

DoorDash Interview Questions on Data Structures

When it comes to answering DoorDash interview questions related to data structures, you should be well-versed with the best, worst, and average runtime complexities for removing, finding, and inserting elements. Topics you must cover include:

• Graphs: Directed and undirected, cyclic and acyclic, BST, and BT (DAGs)
• Stacks
• Queues
• Lists: Doubly linked lists and single linked lists
• Sets
• Arrays
• Hash maps
• Heaps

While other data structures can also be a part of the DoorDash interview questions, you can expect these commonly asked sample questions:

1. Given an array of size N, write a code to print the reverse of the array.
2. How would you implement Stack using Queue?
3. Which Data Structures can be used for implementing LRU cache?
4. How would you convert the Binary tree to DLL in-place?
5. Write a C function to detect a loop in a linked list?
6. Given a String S, write a code to remove successive duplicate characters recursively.

Recommended Reading: Top 20 Interview Puzzles for Software Engineers

DoorDash Interview Questions on System Design

The DoorDash interview questions on system design are for senior software engineer positions. The questions evaluate your ability to build a scalable system with optimal design. You can research and reverse engineer some common systems within your domain to practice for system design questions.

For instance, frontend developers can practice using applications such as Gmail or DoorDash. Backend developers can focus on large systems messenger services. Some sample DoorDash interview questions on system design are:

1. Build a UI component with state management.
2. Design DoorDash from scratch.
3. How would you improve Spotify?
4. How would you uplevel user engagement on the DoorDash app?
5. Design a donation drive system.
6. Describe a recent system you designed of your choice.

Read System Design Interview Preparation Tips to learn about the best approach you can take to solve design problems.

Tips for Answering DoorDash Technical Interview Questions

Here are some important tips to follow to answer DoorDash interview questions with confidence and ace the interview:

• You must have a communicative approach while solving problems to convey your teamwork skills. For example, you can describe key decision steps to the interviewer while answering DoorDash interview questions on coding.
• Clarify your queries (if any) once you get the problem question.  
• Take your time to think about the interview question and construct a coherent solution. You can miss edge cases if you do not clarify the problem with the interviewer. DoorDash also comes up with certain ambiguous questions with a few constraints specifically left out of the question description.
• You must not go with a brute force approach as a final solution.
• The goal is not to get a perfect solution instantly. So ensure that you construct your solution step by step in a logical manner.
• You should have a complete understanding of runtime and in-memory complexities in your approach.  
• For the questions that require you to write unit tests, you should be able to construct concise unit tests.
• You should practice mock interviews to familiarize yourself with the actual interview situation.

DoorDash Case Interview Questions

DoorDash case study interview questions explore your problem-solving abilities and how you can offer actionable insights to the business using your data analytics and data science knowledge.

The interviewer provides you with a dataset and related questions. Datasets usually include details such as drivers, delivery times, money made, and tips. You will have to think of a business problem that DoorDash probably faces that you can tackle with ML.

Next, you have to build a model. Based on the model, you will have to offer solid recommendations to the business. You might have to implement EDA.

Practice these DoorDash case interview questions to prepare yourself:

1. Write a query using SQL that returns a list of the bottom 2% revenue-generating restaurants. Return a list of restaurant IDs and their total revenue from when customers placed orders over a specified period.
2. Write a query that returns the average earnings per hour by day of the week. For calculating the time period, make use of the “Customer placed order date time” field. The “Order total” field is the earnings value.
3. What steps will you take to measure the success of a new grocery delivery business for the firm, given the competition?
4. What would you do as a Product Manager at a food delivery app if there is a 15% decline in restaurant supply over the past week?

Non-Technical DoorDash Interview Questions

DoorDash interview questions also include behavioral and hypothetical situations. Here are some questions for your practice:

1. What would you like to improve about an app that you use regularly?
2. How do you stay up-to-date on the latest trends in the industry?
3. What is your greatest weakness?
4. What are your long-term goals?
5. What are some difficult decisions you have made in your previous role?
6. What is your greatest professional accomplishment?
7. How would you resolve a problem for a client?
8. If offered the position, are you willing to submit to a background check?
9. DoorDash pays utmost attention to customer service. What is your strategy for dealing with demanding customers?
10. What is the biggest thing you learned from a recent project that would influence your performance at DoorDash?
11. What is Agile project management? What makes it different from other project management methodologies?
12. What professional area would you like to improve on?
13. What leadership skills prompt you to choose a tech lead position?
14. What DoorDash facilities make it ahead of its competitors?
15. What unique skills can you contribute to the technical department of DoorDash?

This completes the list of DoorDash interview questions. Here are some frequently asked questions on DoorDash interview prep and the process that you should know for your knowledge.

FAQs on DoorDash Interview Questions

Q1. How do I prepare for DoorDash interview questions?

You should start by scanning DoorDash’s job openings page and understanding the role requirements to prepare well for DoorDash technical interview questions. You can practice coding on a whiteboard or remotely use a shared screen. Working out several sample problems will make the actual interview situation more familiar.

Q2. Are DoorDash interview questions for technical rounds hard?

Interviewees suggest that DoorDash interview questions are of easy-medium level. You should be well-versed in coding, data analysis, and algorithms to ace the DoorDash interview questions.

Q3. How long does it take to hear back after the DoorDash interview?

On average, DoorDash sends the response within a week after the interview process. However, the complete hiring process takes around 2-3 weeks.

Q4. How long does the DoorDash background check take?

According to DoorDash, your background check can take between 5-7 business days. Sometimes, it can take up to 5-10 days for approval.

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