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Backend Developer interview questionsTechnical Interview round
A 60 min interview plan with a time-boxed script, what each question is for, and the signals to score against. Key skills: Backend Technologies, Databases, API Development, Security, Design Patterns.
Backend Technologies
10 min
What this section is for
Purpose
Assess understanding of backend technologies and frameworks.
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Can you explain the differences between REST and GraphQL?
What this question is for, and what to listen for
Purpose
Evaluate knowledge of API development and understanding of different technologies.
Signals to score
- REST and GraphQL differences explained
- Use cases for each mentioned
- Understanding of data fetching
- Knowledge of flexibility in GraphQL
- REST's statelessness understood
- Mention of over-fetching/under-fetching
- Awareness of tooling and libraries
Follow-up questions
- How does REST handle data fetching?
- What are some advantages of using GraphQL?
•
What are some common backend frameworks you have worked with?
What this question is for, and what to listen for
Purpose
Assess familiarity with backend frameworks and practical experience.
Signals to score
- Frameworks like Node.js, Django, etc. mentioned
- Experience with at least one framework
- Understanding of framework strengths
- Mention of community support
- Knowledge of framework scalability
- Awareness of framework limitations
- Practical examples provided
Follow-up questions
- Which framework do you prefer and why?
- Can you give an example of a project using this framework?
Databases
10 min
What this section is for
Purpose
Evaluate knowledge of database systems and data management.
•
How do you decide between using SQL and NoSQL databases?
What this question is for, and what to listen for
Purpose
Assess understanding of database types and decision-making skills.
Signals to score
- SQL and NoSQL differences explained
- Use cases for each type
- Understanding of data structure
- Mention of scalability
- Knowledge of transaction support
- Awareness of flexibility
- Practical examples provided
Follow-up questions
- What are the benefits of using SQL databases?
- Can you describe a scenario where NoSQL is preferable?
•
What are some common database optimization techniques?
What this question is for, and what to listen for
Purpose
Assess knowledge of database performance improvement methods.
Signals to score
- Indexing mentioned
- Query optimization discussed
- Use of caching
- Database normalization
- Partitioning/sharding
- Understanding of load balancing
- Practical examples provided
Follow-up questions
- How does indexing improve performance?
- Can you explain database normalization?
API Development
10 min
What this section is for
Purpose
Assess experience and understanding of API development.
•
How do you ensure the security of an API?
What this question is for, and what to listen for
Purpose
Evaluate knowledge of API security practices.
Signals to score
- Authentication methods explained
- Use of HTTPS
- Rate limiting discussed
- Input validation
- Mention of OAuth
- Awareness of security testing
- Practical examples provided
Follow-up questions
- What is the role of authentication in API security?
- How does HTTPS contribute to security?
•
Can you describe a challenging API you developed and how you overcame the challenges?
What this question is for, and what to listen for
Purpose
Assess problem-solving skills and practical experience.
Signals to score
- Challenge clearly described
- Solution process explained
- Technologies used mentioned
- Collaboration with team
- Lessons learned
- Outcome of the project
- Reflection on improvement
Follow-up questions
- What was the main challenge in this API?
- How did you approach solving it?
Security
10 min
What this section is for
Purpose
Evaluate understanding of security principles in backend development.
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What are some common security vulnerabilities in backend systems?
What this question is for, and what to listen for
Purpose
Assess knowledge of security threats and prevention methods.
Signals to score
- SQL injection mentioned
- Cross-site scripting (XSS)
- Cross-site request forgery (CSRF)
- Data encryption
- Secure coding practices
- Awareness of security patches
- Practical examples provided
Follow-up questions
- How can SQL injection be prevented?
- What is cross-site scripting?
•
How do you stay updated with the latest security practices?
What this question is for, and what to listen for
Purpose
Assess commitment to continuous learning and security awareness.
Signals to score
- Following security blogs
- Attending webinars/conferences
- Participating in security forums
- Reading security whitepapers
- Engaging with security communities
- Awareness of security certifications
- Practical examples provided
Follow-up questions
- What resources do you use to stay informed?
- How often do you update your knowledge?
Design Patterns
5 min
What this section is for
Purpose
Assess understanding of design patterns and their application in backend development.
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Can you explain the Singleton design pattern and its use cases?
What this question is for, and what to listen for
Purpose
Evaluate knowledge of design patterns and practical application.
Signals to score
- Singleton pattern explained
- Use cases mentioned
- Understanding of instance control
- Mention of global access
- Awareness of thread safety
- Practical examples provided
- Limitations discussed
Follow-up questions
- What is the purpose of the Singleton pattern?
- Can you give an example of its use?
Closing
5 min
What this section is for
Purpose
Thanks the candidate for their time, provides next steps, and leaves a positive final impression.
•
Do you have any questions for me about the team or the company?
What this question is for, and what to listen for
Purpose
Gauge the candidate’s curiosity and interest in the role.
Signals to score
- Thoughtful questions asked
- Interest in company culture
- Curiosity about growth expressed
- Questions about role raised
- Inquiries about team challenges
- Engagement with responses shown
- Desire to learn next steps
- Focus on company values expressed
Follow-up questions
- What interests you most about this team?
- Are there any areas of the role you’d like to explore further?
Backend Developer interviews — common questions
- Who is this Backend Developer interview plan for?
- It is written for the interviewer, not the candidate: the hiring manager, engineer or panel member running the Technical Interview round for a Backend Developer role. It gives you a 60 min script to follow in the conversation — 10 questions with what each one is for and the signals to score against — so you are not writing the round from scratch the night before.
- What does the Technical Interview round assess?
- This round is focused on: Backend Technologies, Databases, API Development, Security, Design Patterns. It works through Backend Technologies, Databases, API Development, Security, Design Patterns and Closing, scoring against 65 observable signals, with follow-up prompts on all 10 questions for going deeper where an answer is thin.
- How is the 60 min split up?
- Backend Technologies (10 min), Databases (10 min), API Development (10 min), Security (10 min), Design Patterns (5 min), Closing (5 min). The timings are there so the round stays on schedule and every candidate gets the same shape of interview — which is what makes two candidates comparable afterwards.
- What other rounds should I run for a Backend Developer?
A single round does not cover a whole role. The other rounds in this library for a Backend Developer: