Junior Backend Developer interview questions

How to use these questions

• Start with Screening questions — that's what you'll hear first (recruiter, HR).
• Prepare Technical questions with a concrete case from your experience that proves mastery.
• For Behavioral questions, use the STAR method (Situation, Task, Action, Result).
• Practice out loud — fluency is 50% of interview performance.

Technical (10)

1. 1

   Design REST endpoints for task management (CRUD). What HTTP verbs and status codes?

   Easy

   Scenario — REST API Design

   Tip. GET/POST/PUT/DELETE, 200/201/204/400/404, plural resource naming.

2. 2

   How do you implement pagination and filtering on a REST API?

   Medium

   Scenario — REST API Design

   Tip. Cursor vs offset pagination, query params, total count, performance implications.

3. 3

   Design the database schema for a blog system with authors, posts and comments.

   Medium

   Scenario — Database Design

   Tip. 1:N relationships, foreign keys, indexing, 3NF normalization.

4. 4

   How do you optimize a slow SQL query?

   Medium

   Scenario — Database Design

   Tip. EXPLAIN ANALYZE, adding indexes, avoid SELECT *, pagination, denormalization if needed.

5. 5

   Explain how JWT works and its pros/cons compared to sessions.

   Medium

   Scenario — Authentication & Security

   Tip. Stateless, refresh tokens, expiration, secure storage, revocation challenges.

6. 6

   How do you protect an API against SQL injection and XSS attacks?

   Easy

   Scenario — Authentication & Security

   Tip. Prepared statements/ORM, input validation, sanitization, Content Security Policy.

7. 7

   The API is responding slowly in the morning. How do you diagnose the issue?

   Medium

   Scenario — Debugging & Monitoring

   Tip. Logs, metrics (CPU, memory, DB), slow queries, connection pooling, cold starts.

8. 8

   Describe your approach to debugging a production issue where users are experiencing timeout errors intermittently.

   Medium

   Scenario — Debugging & Monitoring

   Tip. Look for specific examples and data in the candidate's answer. Ask follow-up questions to probe deeper into their reasoning.

9. 9

   How do you test an API endpoint end-to-end?

   Medium

   Scenario — Backend Testing & CI

   Tip. Separate test DB, fixtures, test client, assertions on status/body, cleanup.

10. 10

    What's the difference between unit tests and integration tests? How do you decide which to write for a new feature?

    Medium

    Scenario — Backend Testing & CI

    Tip. Look for specific examples and data in the candidate's answer. Ask follow-up questions to probe deeper into their reasoning.

Behavioral (6)

1. 1

   Describe a situation where you had to collaborate with a difficult team

   Medium

   Scenario — Teamwork & Collaboration

   Tip. Use STAR. Focus on your role as facilitator and results achieved despite difficulties.

2. 2

   How do you handle disagreements within a team?

   Easy

   Scenario — Teamwork & Collaboration

   Tip. Show your listening skills, consensus-seeking and focus on common goal.

3. 3

   Tell me about a professional conflict you resolved

   Medium

   Scenario — Conflict Resolution

   Tip. STAR required. Show empathy, communication and win-win solution.

4. 4

   Tell me about a major conflict you handled at work.

   Medium

   Scenario — Conflict Resolution

   Tip. STAR: situation, both sides' positions, resolution approach, result.

5. 5

   Give an example where you took the lead without being required to

   Medium

   Scenario — Leadership Examples

   Tip. Show initiative, impact and how you brought others along.

6. 6

   Tell me about a situation where you demonstrated leadership without formal title.

   Medium

   Scenario — Leadership Examples

   Tip. Initiative, taking responsibility, mobilizing others, collective result.

Situational (4)

1. 1

   Tell me about a situation with an unhappy client

   Medium

   Scenario — Handling Difficult Clients/Customers

   Tip. STAR. Show active listening, empathy, proposed solution and follow-up.

2. 2

   How do you handle an unhappy client?

   Medium

   Scenario — Handling Difficult Clients/Customers

   Tip. Active listening, empathy, factualizing the problem, concrete action plan.

3. 3

   How did you handle a project with an impossible deadline?

   Medium

   Scenario — Managing Tight Deadlines

   Tip. Show prioritization, proactive communication and value delivery despite constraints.

4. 4

   You have 3 days to deliver what would take you 5. What do you do?

   Medium

   Scenario — Managing Tight Deadlines

   Tip. Negotiate scope, prioritize essentials, communicate transparently.

Leadership (4)

1. 1

   How do you manage an underperforming team member?

   Medium

   Scenario — People Management

   Tip. Show constructive approach: clear feedback, improvement plan, regular follow-up.

2. 2

   Describe your management style.

   Medium

   Scenario — People Management

   Tip. Authentic, examples, awareness of your strengths and watch points.

3. 3

   What is the most important strategic aspect of your last role?

   Medium

   Scenario — Strategic Thinking

   Tip. Vision, structuring choices, long-term impact.

4. 4

   How do you balance short and long term?

   Hard

   Scenario — Strategic Thinking

   Tip. Explicit trade-offs, dedicated resources, communication.

Case Studies (1)

1. 1

   How would you design a real-time notification system?

   Hard

   Scenario — System Design

   Tip. Clarify requirements, propose architecture, discuss trade-offs and scalability.

Screening (2)

1. 1

   Tell me about yourself

   Easy

   Scenario — Tell Me About Yourself

   Tip. Structure: present (current role), past (key background), future (why this role). Max 2 min.

2. 2

   Walk me through your resume

   Easy

   Scenario — Walk Me Through Your Resume

   Tip. Chronological, focus on transitions and progression. Explain career choices.

Negotiations (2)

1. 1

   What are your salary expectations?

   Medium

   Scenario — Salary Negotiation (New Job)

   Tip. Give a market-based range. Justify with your added value.

2. 2

   Which elements of the package are most important to you?

   Easy

   Scenario — Compensation Package Discussion

   Tip. Be honest but flexible. Show you understand total compensation.

Cultural Fit (2)

1. 1

   What type of work environment allows you to perform at your best?

   Easy

   Scenario — Company Culture Alignment

   Tip. Be authentic but align with company culture (if you know it).

2. 2

   What attracts you to our company culture?

   Easy

   Scenario — Company Culture Alignment

   Tip. Prior research, aligned values, concrete examples.

Career Dev (2)

1. 1

   How did you handle an internal job change?

   Medium

   Scenario — Internal Transfer Discussion

   Tip. Honesty, transparency with old manager, clean transition.

2. 2

   Why an internal transfer rather than leaving?

   Easy

   Scenario — Internal Transfer Discussion

   Tip. Cultural continuity, internal opportunity, leveraging existing knowledge.

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