HM BQ: The hiring manager was very nice and kept asking follow-up questions about the impact.

Branding Round: I worked on a file system and had to implement a Trie tree. I talked a bit about OOP fundamentals. I managed to write the solution with some difficulty — the codebase was quite large and I didn’t write tests. Follow-up questions: how to handle multithreading, and how to serialize.

System Design: They dug deep into my recent project. The system design topic was messaging. They asked follow-up questions about the schema and how messages are sent.

Debugging: This was also a high-frequency question (felt like this was the question). The follow-ups didn’t seem to have a single standard answer — I talked about multithreading, edge cases, and monitoring.
You can refer to other DoorDash interview experiences; the difficulty is generally manageable, and they often repeat questions.