What I Learned from 8 Backend Interviews: Real Stories and Technical Insights

1. Afanti

First interview at a K12 online education company. The written test covered basic Python concepts such as mutable vs immutable objects and garbage collection, plus a simple data‑modeling question.

Second interview focused on self‑introduction, project experience, and system‑design basics. The interview went well and led to a third round with the CTO.

Third interview with the CTO covered a wide range of topics, from server deployment to Nginx details. The most memorable question was: "Describe in detail what happens from the moment a browser sends a request to when it receives a response."

Answer summary:

Network model: client (browser) communicates with server via HTTP over TCP (or HTTPS with TLS/SSL). Below TCP are routing protocols (OSPF), data‑link layer (ARP/RARP), and physical layer (IEEE 802.x).

When a request is sent, the client packages data, resolves IP‑MAC mapping, performs DNS lookup, routes through n hops, and establishes TCP three‑way handshake.

Application layer: HTTP is stateless; discuss GET/POST, RESTful design, server models (epoll, select). Example flow: Nginx receives request, performs validation, serves static resources directly, forwards dynamic requests to uWSGI, which passes the WSGI environ to Django, runs middleware, executes view logic, builds response, and returns through uWSGI and Nginx to the browser.

2. Xuetang Online

Interview process similar to Afanti, with a backend engineer conducting the first round (resume, project experience, simple algorithms, Python basics). The second round involved system‑design questions; the candidate’s Django experience helped pass.

3. Guokr

First round required a detailed registration form, then a written test with Python basics, database queries, and a classic O(1) stack problem (push, pop, get max/min). The candidate discussed a flawed O(1) solution and later refined it.

Second round focused on pure technical questions, including TCP flow control (the candidate mistakenly mentioned congestion control). The interview ended with database fundamentals, highlighting the importance of understanding indexes and storage engines.

4. Veeva

Phone interview followed by a homework assignment (leap‑year function). The candidate submitted a well‑structured, object‑oriented solution with tests.

Subsequent rounds covered Python/Django basics, a live coding exercise, and a system‑design task to create a short‑URL service with collision avoidance.

5. Zhihu

Multiple rounds included project discussion, basic algorithms (quick sort, binary search), TCP, epoll, Tornado internals, and a design question about WeChat red‑packet architecture.

6. Chunyu Doctor

First round involved practical coding tasks based on real product scenarios, followed by system‑design of a QQ‑like chat tool and database discussion.

7. 360

First round combined a Python written test with Linux basics; the candidate struggled with advanced Linux commands.

Second round featured Python debugging, lambda expressions, and a stack‑using‑two‑queues implementation. The interview highlighted a mismatch between the candidate’s Python experience and the role’s expectations.

8. ByteDance (Toutiao)

First round included a Python coding test (Fibonacci function) and questions on Redis usage, hash‑table collisions, and TCP.

def fib(n):
    a, b = 0, 1
    for x in xrange(n):
        a, b = b, a + b
    return b

Second round asked about cache‑miss handling and a linked‑list reversal problem.

def revese(node):
    p = node
    cur = node.next
    p.next = None
    while cur:
        tmp = cur.next
        cur.next = p
        p = cur
        cur = tmp
    return p

Later rounds focused on system‑design (multi‑device login, QR code login) and final HR discussions leading to an offer.

Summary

The author ultimately accepted the offer from ByteDance after a lengthy interview journey spanning multiple companies. The article emphasizes the value of solid Python fundamentals, database knowledge, system‑design practice, and leveraging personal projects to stand out in technical interviews.