Interview Preparation Guide: Algorithms, Theory, Backend Technologies, and Real Interview Questions

1 Interview Preparation

1. Algorithms

Every technical interview at Toutiao includes algorithm questions. I first quickly reviewed "JianZhi Offer" (which I had already covered during campus recruitment) and then tackled LeetCode problems. Because the volume is large, I focus on categories, solving a few representative problems per type, such as using recursion and two‑pointer techniques for linked‑list questions, two stacks or queues for stack/queue problems, and recursion for tree problems. Array and string problems are more flexible and require extensive practice.

When I cannot code at work, I read the problem on the LeetCode website via phone, mentally outline the solution, and write code only if I can picture it. If I get stuck, I glance at others' solutions. This fast‑review method works because interviewers care mainly about the core idea and correct boundary handling rather than a fully polished implementation.

2. Theory Fundamentals

Rapidly review language basics (I use C++), operating systems, and network programming.

OS topics: memory management, process management, file systems, especially virtual memory.

Network programming: TCP/IP (three‑way handshake, four‑way termination, TIME_WAIT), HTTP (status codes, methods), and web security (HTTPS encryption details, XSS, CSRF, SQL injection).

3. Backend Technologies

Prepare core backend components and architecture: MySQL, Redis, message queues, Zookeeper, distributed system design, and Docker.

4. Deep‑Dive Projects

Even without open‑source experience, highlight project strengths:

Identify standout features, e.g., implementing a delayed queue with Redis and sharding to alleviate bottlenecks.

Point out complex parts of the project, even if you didn’t design them, provided you understand them well.

Quantify improvements, such as reducing an API’s TP99 latency from 500 ms to 200 ms.

Show how you enabled the team, e.g., building a reusable tool or service that added value across the group.

2 Interview Questions

1. First Round

Project discussion

How does the task system guarantee reward delivery after task completion?

Implementation of a ZSET delayed queue

Redis data structures and their implementations

Redis persistence mechanisms

MySQL indexing concepts

Algorithm: Find a maximum‑sum subsequence where chosen elements are non‑adjacent in the original array

2. Second Round

Detailed explanation of Redis ZSET implementation (skip‑list + hash + compressed list)

Ranking with equal scores sorted by time: split score into high‑32‑bit (score) and low‑32‑bit (timestamp) or other methods

MySQL transaction isolation levels and associated issues

Differences between binlog and redolog, two‑phase commit

C++ dynamic polymorphism implementation

Can a constructor be virtual in C++?

LeetCode 41 – first missing positive integer

Can an opened file be deleted by another process in Linux?

Choosing TCP vs. UDP for sending a 10 MB buffer with possible packet loss

Protocols involved in a complete HTTP request

3. Third Round

Project discussion

Redis ZSET implementation recap

Design a rate‑limiting system (token bucket)

Design a delayed‑task system: Redis ZSET with sharding and persistence, or a time‑wheel approach

Generate a uniform 0‑6 random number using a 0‑4 generator

Game theory: N chess pieces, each turn take 1‑M pieces; determine winning strategy for 1000 pieces with max 8 per turn

Find lowest common ancestor for given nodes in a binary tree

4. Fourth Round

HR interview.

3 Summary

All four interview rounds were conducted via video, which felt comfortable at home; however, nervousness can hinder thinking.

Toutiao repeatedly asked about ZSET implementation, so reviewing the source code is beneficial; merely mentioning a skip‑list is insufficient.

When faced with unfamiliar logic or algorithm questions, don’t give up—ask the interviewer for hints; progressing with guidance is still valued.

Interview question collection: Java Interview Question Repository

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