Cracking the DoorDash Software Engineer Intern Interview: Design Challenges & Insights

Software Engineering
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doordash | Software Engineer Intern | Interview Experience

Interview Date: Not specified
Result: Not specified
Difficulty: Not specified

Interview Process

The interview process consisted of four rounds. The recruiter informed that if a candidate clearly fails in any round, they would promptly announce the result and cancel the subsequent interviews.

  1. First Round: Conducted by a friendly interviewer from the U.S. who frequently reminded the candidate of the question requirements and guided them towards the expected content. The design question was to create a flight ticket booking system for a Grammy event. The system was to only book tickets for the same day, with round-trip tickets available between City A and City B. There were 100 one-way tickets available each day. The goal was to produce a table that clearly displayed how many tickets agent X purchased on day N.

    The interviewer emphasized three main requirements:

    1. Design the API
    2. Design the database and corresponding tables
    3. Write SQL or pseudocode

  2. Second Round: Focused on coding, specifically on a rate limiter and a pub/sub model. The rate limiter required an explanation of various algorithms, comparing their advantages and disadvantages. The interface was straightforward, but the interviewer also delved into deeper Java concepts, which made it challenging. The pub/sub model provided only a basic subject and subscription framework, with minimal interface details, requiring the candidate to fill in much of the code themselves.

  3. Third Round: A project deep dive with a director from India. After some small talk, the candidate began presenting their project. However, the performance was not strong, as it was the candidate’s first time presenting a project. The presentation lasted from the 15th minute to about the 45th minute, after which the interviewer shifted to a Q&A session. The responses were largely formal and lacked substantive depth.

After completing the three rounds in the morning and one in the afternoon, the recruiter notified the candidate about ten minutes after the last interview that they had not passed and canceled the upcoming CTO interview.

Technical Questions

  1. Design a flight ticket booking system (System Design, Database, API Design)
  2. Rate Limiter (Algorithms, Design)
  3. Pub/Sub Model (Message Queuing, Design)

Tips & Insights

  • Be prepared to explain design choices and algorithms in depth.
  • Practice presenting projects clearly and concisely, as first impressions can significantly impact the interview outcome.