Inside Top Chinese Tech Interviews: Backend Engineer Questions & Answers

WeChat Backend Engineer Interview

First round: six algorithm problems (linked list, binary tree, longest common substring) to be solved in ~40 minutes, plus questions on key/value cache implementation, load bottlenecks, Tencent gaming backend load‑balancing architecture, disk‑performance tuning (top, iostat), coding standards, TCP/UDP trade‑offs, reliable UDP transmission, network debugging tools (tcpdump, lsof, netstat), compiler implementation and Chinese encoding, process inspection (top, /proc/pid), function‑frequency profiling with valgrind.

Second round: director asked for self‑introduction, best project (compiler), UDP file‑transfer service, UDP reliability details, motivation for speed advantage over SCP, reading habits (Linux kernel), memory concepts, mmap and direct I/O, advantages and drawbacks.

Third round: HR interview, self‑introduction, offer count, willingness to stay in Guangzhou, discussion of most outstanding project.

Result: offer received.

NetEase Game Engineer Interview

Written test: three‑hour exam with 30 basic questions and six algorithm problems (array traversal, non‑recursive algorithms, BNF, linked list, graph, Bloom filter). Candidate felt insufficient flexible knowledge.

First interview: matrix multiplication test, C++ self‑introduction, polymorphism example, TCP protocol, epoll characteristics (LT vs ET), process memory layout, BFS, segment tree, nearest‑point algorithm with integer preprocessing, compiler implementation discussion.

Second interview: card‑24 puzzle, algorithmic solution, random point placement in a sector (angle‑radius method, area‑based distribution, continuous density function), random shuffle proof, compiler recap, candidate declined further HR round.

Result: offer received.

Kingsoft West Mountain Residence Interview

First interview: C++ questions on new/delete vs malloc/free, undefined behavior of delete on new‑allocated array, memory allocation error despite 1 GB free, class constructor order, TCP sticky‑packet phenomenon (Nagle algorithm, application‑layer framing), a brain‑teaser about coal‑train logistics.

Second interview: 3D mobile game director asked about compiler knowledge, practical approach, multithreading concerns, FTP purpose.

Third interview: CTO asked about function declaration vs definition, compiler discrimination, Tencent internship concurrency strategy (multi‑CPU network interrupts, special NICs, newer Linux), coding habits, career aspirations, game industry insights (Unreal Engine limitations, cloud wind, Xiaomi).

Result: offer accepted then declined after advice on choosing between WeChat and NetEase.

Renren Backend Engineer Interview

First interview: de‑duplication algorithm for string “aabbbccddff”, Tencent internship disk‑efficiency question, UDP reliable transmission, O(1) stack max‑element algorithm (not solved).

Second interview: irregular polygon wood‑cutting problem solved with Huffman algorithm, Linux memory and disk queries, ls usage.

Third interview: key/value store pros/cons, distributed mapping via central proxy, lock‑free max‑value update technique, finding k‑th largest number in massive data (bucket partition, bit filtering, k‑heap, multi‑machine external sort).

Result: offer received.