Backend Interview Questions
Interview question bank for evaluating backend engineering candidates.
Interview Process
Section titled “Interview Process”- Round 1: Select questions from below to assess candidate’s technical foundation
- Round 2: Deep dive into resume projects to evaluate technical depth, communication, and teamwork
- Final Round: Focus on non-technical qualities and compensation
Evaluation Dimensions
Section titled “Evaluation Dimensions”- Knowledge depth and breadth: Current technical expertise
- Growth potential: Learning ability and future development
- Culture fit: Personality, work attitude, communication style
Foundation Questions
Section titled “Foundation Questions”- How do you learn new technologies?
- Have you contributed to open source? In what way?
- Describe a memorable bug you solved and the debugging process.
- What is a Trait? How does it differ from class inheritance? How to resolve naming conflicts?
- What interfaces does PHP provide for autoloading? What is PSR-4?
- What is
yield? What are common use cases?
Laravel
Section titled “Laravel”- Laravel is known for poor performance. Where are the bottlenecks and how to optimize?
- How does Auth (Authentication and Authorization) work? What auth methods does Laravel’s Auth module support?
- How do you use the Routing module? (Advanced: Explain the routing implementation flow)
- What happens during Laravel framework bootstrap? How is dependency injection implemented?
- Which design patterns are you familiar with?
- What is PHP’s session mechanism? What about Laravel’s?
- What ORM model relations exist in the Database module? How do you use it? (Advanced: Explain the database implementation)
Database
Section titled “Database”- How to analyze SQL query performance?
- What are index optimization principles?
- Difference between primary key index and regular index?
- Transaction isolation levels?
- What data structures are commonly used?
- Which Redis data structure implements Laravel queues?
Networking
Section titled “Networking”- Difference between HTTPS and HTTP? What cryptographic concepts are used (symmetric/asymmetric encryption, digest algorithms, signatures)?
- Public key vs private key encryption - when to use each?
- Equivalent question: Does HTTPS use symmetric or asymmetric encryption for data transfer? Why?
- What are HTTPS optimization/acceleration techniques?
- What HTTP methods exist? (Expect: GET, POST, PUT, DELETE; bonus: OPTIONS, PATCH)
- Difference between POST, PUT, and PATCH?
- What happens when you enter a URL in a browser until the page displays?
- Common status codes and their meanings? 5xx troubleshooting approaches?
Security
Section titled “Security”- Explain web injection attacks. What are the two most common (XSS and CSRF)? How to prevent them?
TCP/IP
Section titled “TCP/IP”- Which layer does TCP belong to? (Physical → Data Link → Network (IP) → Transport (TCP) → Application (HTTP))
Protocols
Section titled “Protocols”- Familiar with OAuth 2.0? What Grant Types exist and their differences?
- Describe the OAuth Authorization Code Grant flow in detail.
- What parts compose a JWT? What does each part do?
- How to let a third party verify JWT token validity?
RESTful
Section titled “RESTful”- Briefly describe RESTful architecture.
- What commands do you commonly use?
- Difference between hard links and soft links?
- Permission notation (e.g., 0700, 0655) - what do these numbers mean? What permission is needed to enter a directory?
- In bash, what does “1>&2” at the end of a command mean?
- What Git workflow does your company use? Have you used gitflow?
- What does
rebasedo? (Basic) What aboutcherry-pick? (Advanced) When would you use them? - How do you resolve conflicts during merge or rebase?