What Do Top Tech Companies Really Test in Linux Server Engineer Interviews?

1. Data Structures and Algorithms

Many IT companies, especially Baidu and iQIYI, start with a quick review of your background and then dive straight into algorithm and data‑structure problems. Typical topics include:

Quick sort : discuss steps, average/ best/ worst‑case complexity; a description is usually enough for senior hiring.

Binary search : write the algorithm or apply it to a concrete scenario such as computing a square root.

Linked lists : delete a node, reverse a list, find intersection of two lists, and handle edge cases like null pointers.

Implement basic functions : re‑implement strcpy, memcpy, memmove, atoi with correct handling of dynamic memory.

Hash tables : design insertion algorithm for arbitrary‑type elements, discuss collision handling and hash functions.

AVL, B‑tree, Red‑Black tree : explain concepts, complexity, rotations, and how they relate to database indexes (e.g., MySQL).

Interviewers pay close attention to code style, boundary checks, and correctness of return values (e.g., returning the new head after list reversal).

2. Operating‑System Principles and Core Technologies

This group of companies—such as Ele.me, Bilibili, Ximalaya, 360, and Ctrip—combine algorithm questions with deeper system knowledge.

Fundamental C++ topics often asked:

Purpose of virtual in inheritance, destructor behavior, and object layout in multiple inheritance (diamond problem).

Use cases for static, static_cast, reinterpret_cast, dynamic_cast.

Virtual‑table layout and how many vtables a class with diamond inheritance has.

Common C++11/14 features that interviewers expect you to know: auto, range‑based for loops.

R‑value references and move constructors. std::forward, std::move.

Container methods like emplace_back, std::thread, std::chrono.

Smart pointers ( shared_ptr, unique_ptr, weak_ptr) and their implementation principles.

Thread‑synchronization primitives ( std::mutex, std::condition_variable, std::lock_guard).

Lambda expressions and std::function / std::bind.

Network communication questions focus on TCP/IP stack details, three‑way handshake, four‑way termination, socket API usage, and edge‑case states such as CLOSE_WAIT and TIME_WAIT. Example from Bilibili:

A and B have an established connection but never exchange data. B suddenly reboots. What TCP state is A in, and how can the server program clear that state?

Other frequent topics include congestion control, packet header fields, blocking vs. non‑blocking sockets, Nagle/keep‑alive/linger options, TCP vs. UDP differences, epoll vs. select (level‑triggered vs. edge‑triggered), and designing protocols to avoid packet “sticking”.

Operating‑system fundamentals often explored:

ELF file sections and their mapping to process address space.

Location of global and static variables in memory.

Protected mode vs. real mode, interrupt vector tables, and CAS instructions on Linux.

Daemon processes, zombie processes, and how they are created and reaped.

Stack vs. heap differences, stack frame layout, calling conventions (__cdecl, __stdcall, __thiscall, __fastcall), and why variadic functions like printf cannot use __stdcall.

Process vs. thread distinctions, synchronization mechanisms (mutex, semaphore, condition variable), deadlock causes and avoidance.

Inter‑process communication methods on Linux: shared memory, anonymous and named pipes, sockets, message queues.

3. Project Experience

Interviewers often ask you to describe past projects that match the target role. For senior or managerial positions, they may probe deeper into domain‑specific experience (e.g., game development, trading systems). Demonstrating relevant project work can fast‑track you to the offer stage.

4. Unreliable Companies (What to Watch Out For)

Four typical problematic company types emerged from the author’s experience:

“Show‑off” companies : overly long interview processes, mixed technical depth, and vague role descriptions.

“Zen” companies : friendly interviewers but low salary offers and unclear hiring intent.

“Paper‑work” companies : excessive document verification, long waiting periods, and modest compensation.

Disrespectful companies : mismatched interviewers (e.g., junior staff interviewing senior candidates) and irrelevant nit‑picking questions.

5. Concerns Beyond Technical Skills

When evaluating a job offer, consider the following non‑technical factors:

If you are early in your career, prioritize technical growth over a small salary gap; be open to role transitions (e.g., C++ → Java).

Salary expectations that exceed the advertised range may still lead to rejection, even after flawless interview performance.

Interviewing at companies you are not keen on can still provide valuable experience.

Assess the interviewers: if you can answer ~80% of their questions, the company likely offers a good learning environment.

Clarify future responsibilities to avoid being assigned unwanted tasks.

If you encounter a question you cannot answer, ask for hints or discuss your thought process instead of giving up.

Do not underestimate written tests that include mathematical or logical puzzles.

Maintain confidence; every candidate’s background is unique.

The author hopes that sharing experiences from more than 30 interview rounds will help readers navigate technical interviews more effectively.