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

Background: The author graduated in 2015 from a 985 university’s communications engineering department, spent time on personal startups, and began applying for corporate positions in late 2016 with only one year of work experience.

1. Afanti (K12 online education)

First round: a written test on Python basics, mutable vs immutable objects, garbage collection, and a simple database design question.

Second round

Technical discussion on the author’s projects, system design basics, and deeper Python questions.

Third round (CTO)

The CTO asked for a detailed explanation of a browser request lifecycle. The answer covered:

Network model: client‑server communication via HTTP (application layer) over TCP (transport layer), optional TLS/SSL (session layer), routing protocols (OSPF), ARP/RARP for IP‑MAC resolution, and physical layer standards.

Application layer: HTTP’s stateless nature, GET/POST differences, RESTful design, Nginx handling static resources, forwarding to uWSGI, uWSGI communicating with Django via the WSGI interface, Django middleware processing, view execution, response construction, and returning through Nginx to the browser.

2. XueTang Online (MOOC platform)

Three‑stage interview focusing on Python fundamentals, project experience, system design, and basic algorithms. The author received an offer.

3. Guokr

Technical interview emphasized database design, SQL queries, and a classic O(1) stack problem (supporting push, pop, max, min). The author discussed the difficulty of achieving O(1) for max/min and referenced common solutions.

4. Veeva (CRM for biotech)

Phone screen, a homework assignment to implement a leap‑year check (used to demonstrate clean, testable code), followed by Python/Django questions and a system design task to generate short URLs with collision avoidance.

5. Zhihu

Multiple rounds covering project experience, Python basics, quicksort implementation, TCP, epoll, Tornado internals, database fundamentals, and a design exercise for a WeChat red‑packet system.

6. Chunyu Doctor

Interview focused on practical coding tasks (e.g., grouping doctor‑patient chat records), Python/Django basics, and a system design for a QQ‑like chat application with group management.

7. 360 (Security)

Written test combined Python questions with Linux fundamentals; the author struggled with advanced Linux topics. Subsequent rounds included Python debugging, lambda expressions, a queue‑based stack implementation, and discussion of the author’s open‑source serializer project.

8. Toutiao (ByteDance)

First round: Python coding (including a Fibonacci function) and questions on Redis usage, hash‑table distribution, TCP, and algorithmic complexity. The author provided the following code:

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

Second round: system design for cache‑stampede mitigation and a linked‑list reversal problem, with the author’s solution:

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

Subsequent rounds involved multiple system‑design questions (multi‑device login, QR‑code login) and final HR discussions leading to an offer with generous benefits.

Conclusion

The author ultimately accepted the Toutiao offer, reflecting on the importance of leveraging campus recruitment, building personal projects, and continuously practicing interview problems such as those on LeetCode.