ByteDance New Grad Software Engineer Interview Experience — Backend Fundamentals, Databases, and One DFS Problem

First round: technical interview. The interviewer was based in China.

The interview leaned toward backend fundamentals, databases, middleware, and web protocols, followed by one algorithm problem.

1. Deep dive into resume projects

The interviewer asked about past projects on my resume, focusing on project architecture, the reasons for technical choices, and implementation details from the business logic.

2. Middleware: Kafka and Message Queues

I was asked about Kafka and the principles and characteristics of message queues.

3. MySQL indexes

The questions covered the leftmost-prefix principle for composite indexes and why a covering index can improve query speed, including how it works underneath.

4. Cache problems

I was asked about cache breakdown: what it is, why it happens, and how to solve it.

5. Web protocols

I had to introduce RESTful APIs, their design conventions, and their basic form, then compare WebSocket with server-sent events. There was also a project-scenario question: when building an AI agent runtime, why did I choose ordinary web calls instead of WebSocket? This tested whether the technology choice fit the business scenario.

6. Database architecture migration

The scenario was a migration from MySQL to MongoDB. Why would we make that move? How did the architectures compare, what benefits did the migration bring, and how much did performance improve?

I did not answer this well. I did not understand the applicable scenarios and architectural differences between the two databases well enough, so I still needed to strengthen my understanding of SQL versus NoSQL selection.

7. Algorithm problem

Most of the interview time went into my resume. At the end, there was a token LeetCode-style question: reconstruct a binary tree from its preorder and postorder traversals using depth-first search.