E4 at DoorDash

How it went

What they would tell you

How to prepare

Round by round

1. 1

   Telephonic Round10 min

   Quick introduction and then jumped into some API-related question, the conversation was short & to the point

2. 2

   Design (LLD)60 min

   Began by asking about my past project, where I had built a Food Ordering System, discussed the project in detail covering the core features, system flow, and the tech stack I used for both frontend and backend development. Later, he asked me to suggest new features I could add to improve the system

3. 3

   HM Round60 min

   The manager started by asking about projects

   • Discussed my current project
   • Past projects
   • My specific role in making it
   • Hardest challenges
4. 4

   Debugging Round60 min

   You’re given a simplified load balancer implementation that stores active servers in a list and picks the next one using (index + 1) % len(list). However, some servers go down intermittently. The interviewer asked me to debug why requests are occasionally being routed to inactive servers and to suggest a fix to make it efficient Follow-ups

   • How would you handle concurrent updates when multiple threads mark servers as unhealthy?
   • Can you optimize selection for large server lists?

What came up