What Tech Companies Really Test in Server Developer Interviews – Insights from 30+ Companies

1. Data Structures and Algorithms Focus

Many IT companies, such as Baidu and iQiyi, start with a brief review of your background and then dive straight into algorithm and data‑structure problems. Typical topics include quicksort (explain steps and complexity), binary search (often with a concrete scenario), linked‑list operations (delete a node, reverse a list, find intersection), and implementing basic functions like strcpy, memcpy, atoi. Interviewers also probe hash tables, AVL/B‑trees, and red‑black trees, checking your understanding of concepts, complexity, and implementation details.

Quick sort : discuss algorithm steps and average/worst‑case complexity.

Binary search : explain usage scenarios and implementation.

Linked list : write deletion, reversal, intersection algorithms.

Basic functions : implement strcpy, memcpy, atoi correctly.

Hash table : insertion algorithm, collision handling, hash function design.

AVL/B‑tree : concepts and, for MySQL, index implementation.

Red‑black tree : structure, rotations, and complexity.

2. Operating‑System Principles and Core Technologies

This track, common in companies like Ele.me, Bilibili, and Huawei, blends algorithm questions with deeper system knowledge. Topics include C++ virtual functions, destructor rules, multiple inheritance layout, static keyword, casting operators, and virtual table layout. Interviewers also ask about C++11 features (auto, range‑for, rvalue references, std::move, std::forward, emplace_back, thread library, smart pointers, std::function, etc.).

Network‑communication questions are frequent: TCP/IP stack layers, three‑way handshake, TCP states (e.g., CLOSE_WAIT, TIME_WAIT), socket options (Nagle, keepalive, linger), differences between select and epoll, and HTTP GET vs POST. Sample question – “If a TCP connection is established and the peer reboots, what state is the local socket in and how to clear it?”

Operating‑system fundamentals also appear: ELF sections and their mapping, global/static variable placement, protection vs real mode, interrupt vectors, CAS, daemon vs zombie processes, stack vs heap differences, calling conventions (__cdecl, __stdcall, etc.), and inter‑process communication mechanisms (shared memory, pipes, message queues, sockets).

Open‑source technologies are examined as well. Experience with Redis (data structures, rehash, transactions, clustering) and MySQL indexing is often expected, especially for backend roles.

3. Project Experience Evaluation

Interviewers may simply verify that your past projects align with the target position. For senior or managerial roles, deeper technical depth is expected; otherwise, matching experience is sufficient to get the job.

Unreliable Company Types

The author categorises problematic employers into several types:

Show‑off companies : overly long interview processes, irrelevant high‑level questions, and vague role descriptions.

“Buddha” companies : friendly interviewers but low salary offers.

“Old‑lady‑wrap‑feet” companies : excessively bureaucratic, demanding many documents, and offering poor compensation.

Disrespectful companies : assign junior interviewers to senior candidates, ask trivial or irrelevant questions, or waste time with unprepared interviewers.

Beyond Technical Skills

Additional considerations include career growth potential, realistic salary expectations, the value of interviewing even with companies you may not join, assessing the interviewer's competence, clarifying future responsibilities, handling unknown questions gracefully, and not underestimating written‑test puzzles.

Overall, the article summarises practical insights gathered from interviewing at more than thirty companies, aiming to help readers prepare effectively for technical interviews and make informed career decisions.