Effective Work Sample Exercises for Hiring Top Backend Engineers

Backend engineering forms the foundation of any successful software application. The server-side logic, database architecture, and API design created by backend engineers directly impact application performance, scalability, and reliability. Finding the right backend talent is critical, as these professionals build the systems that power your entire technology stack.

Traditional interviews often fail to reveal a candidate's true capabilities. While technical questions can assess knowledge, they rarely demonstrate how engineers apply that knowledge in real-world scenarios. This is where carefully designed work samples become invaluable. By observing candidates tackle authentic engineering challenges, you gain insight into their problem-solving approach, code quality, architectural thinking, and communication skills.

The exercises outlined below are specifically crafted to evaluate the core competencies required for backend engineering excellence. They assess not just technical proficiency but also the candidate's ability to make sound architectural decisions, troubleshoot complex issues, and collaborate effectively with team members. These samples move beyond theoretical knowledge to reveal how candidates perform when faced with the types of challenges they'll encounter in your organization.

By implementing these work samples in your hiring process, you'll be able to objectively compare candidates based on demonstrated skills rather than interview performance alone. This approach reduces bias, improves hiring accuracy, and helps identify engineers who will truly excel in your environment. Additionally, candidates appreciate the opportunity to showcase their abilities in realistic scenarios, creating a more engaging and respectful interview experience.

Activity #1: API Design and Implementation Challenge

This exercise evaluates a candidate's ability to design and implement a RESTful API endpoint, demonstrating their understanding of API best practices, code organization, error handling, and database interactions. These skills are fundamental for backend engineers who will be responsible for creating and maintaining the services that power your applications.

Directions for the Company:

• Provide the candidate with a clear specification for a simple API endpoint that needs to be implemented (e.g., an endpoint to manage user profiles, product inventory, or event registrations).
• Supply a basic project structure with the necessary dependencies already configured to save time.
• Include any relevant database schemas or mock data the candidate should work with.
• Allow 60-90 minutes for completion, depending on the complexity of the task.
• Consider providing access to documentation or allowing internet searches, as this reflects real-world working conditions.
• Have a senior engineer available to answer clarifying questions, just as they would in a real work environment.

Directions for the Candidate:

• Design and implement the specified API endpoint according to RESTful principles.
• Include proper input validation, error handling, and appropriate HTTP status codes.
• Write clean, efficient code with meaningful variable names and comments where necessary.
• Implement the required database interactions (queries, updates, etc.).
• Be prepared to explain your design decisions and any tradeoffs you considered.
• If time permits, include basic unit tests for your implementation.

Feedback Mechanism:

• After reviewing the implementation, provide specific feedback on what the candidate did well (e.g., clean code structure, thoughtful error handling, efficient database queries).
• Offer one constructive suggestion for improvement (e.g., better validation, more robust error handling, query optimization).
• Give the candidate 15 minutes to refactor their code based on the feedback, observing how they incorporate suggestions and their ability to quickly improve their work.

Activity #2: System Design and Scalability Planning

This exercise assesses a candidate's ability to think architecturally and design scalable systems—a critical skill for backend engineers who must build applications that can grow with your business. It reveals how candidates approach complex problems, make technical tradeoffs, and communicate their thinking.

Directions for the Company:

• Create a realistic scenario describing a system that needs to be designed (e.g., a notification service, data processing pipeline, or authentication system).
• Include specific requirements around scale, performance, and reliability.
• Provide a whiteboard or collaborative diagramming tool for the candidate to use.
• Allocate 45-60 minutes for this exercise.
• Have a senior engineer or architect participate to ask probing questions and evaluate the candidate's reasoning.
• Prepare specific questions about handling edge cases, failure scenarios, and scaling challenges.

Directions for the Candidate:

• Design a high-level architecture for the described system, including major components and their interactions.
• Explain how your design addresses the specified requirements for scale and performance.
• Identify potential bottlenecks and how you would address them.
• Discuss data storage considerations and any caching strategies you would implement.
• Be prepared to explain how your system would handle failure scenarios.
• Consider operational aspects such as monitoring, deployment, and maintenance.

Feedback Mechanism:

• Provide feedback on the strengths of the candidate's design (e.g., thoughtful consideration of scalability, good component separation).
• Suggest one area where the design could be improved or a consideration that was overlooked.
• Ask the candidate to revise a specific portion of their design based on the feedback, observing how they incorporate new information and adapt their thinking.

Activity #3: Debugging and Troubleshooting Exercise

This exercise evaluates a candidate's problem-solving abilities and debugging skills—essential qualities for backend engineers who will inevitably encounter complex issues in production systems. It reveals how candidates approach unfamiliar code, diagnose problems, and implement effective solutions.

Directions for the Company:

• Prepare a small, self-contained application or service with intentionally introduced bugs or performance issues.
• The issues should be realistic and varied (e.g., a memory leak, inefficient database query, race condition, or improper error handling).
• Provide the candidate with access to the codebase, any necessary tools, and a brief description of the reported symptoms.
• Allow 45-60 minutes for the exercise.
• Include relevant logs or error messages that would typically be available in a real troubleshooting scenario.
• Have a developer familiar with the codebase available to answer environment-specific questions.

Directions for the Candidate:

• Review the provided application and identify the issues causing the reported symptoms.
• Use appropriate debugging tools and techniques to diagnose the problems.
• Document each issue you find, explaining the root cause and its impact.
• Implement fixes for the identified issues, prioritizing them based on severity.
• Be prepared to explain your troubleshooting process and reasoning behind your solutions.
• Consider not just fixing the immediate issues but also preventing similar problems in the future.

Feedback Mechanism:

• Provide feedback on what the candidate did well in their troubleshooting approach (e.g., systematic investigation, effective use of debugging tools).
• Suggest one area where their approach could be improved or a bug they may have missed or incompletely fixed.
• Give the candidate 15 minutes to address the feedback, observing how they adapt their approach and implement a more complete solution.

Activity #4: Technical Planning and Estimation Collaboration

This exercise assesses a candidate's ability to break down complex tasks, estimate work accurately, and communicate technical details effectively—skills that are crucial for successful collaboration in engineering teams. It reveals how candidates think about project planning and how they interact with team members.

Directions for the Company:

• Create a realistic feature request or technical project description that would typically be assigned to a backend engineer.
• Include business context and high-level requirements without specifying implementation details.
• Arrange for 1-2 team members to participate in a planning session with the candidate.
• Allocate 45-60 minutes for this exercise.
• Prepare questions about dependencies, risks, and technical approaches to evaluate the candidate's thinking.
• Have participants ready to play roles such as product manager, fellow engineer, or technical lead.

Directions for the Candidate:

• Review the feature request or project description provided.
• Break down the work into logical tasks or components.
• Estimate the effort required for each task and identify any dependencies.
• Discuss potential technical approaches and their tradeoffs.
• Identify any risks, challenges, or areas requiring further clarification.
• Collaborate with the team members to refine the plan based on their input.
• Document the agreed-upon approach and next steps.

Feedback Mechanism:

• Provide feedback on the strengths of the candidate's planning approach (e.g., thorough task breakdown, realistic estimations, good risk identification).
• Suggest one area where their planning could be improved (e.g., overlooked dependency, underestimated complexity).
• Ask the candidate to revise a specific portion of their plan based on the feedback, observing how they incorporate new considerations and adjust their approach.

Frequently Asked Questions

How long should we allocate for these work sample exercises?

Each exercise is designed to take 45-90 minutes, depending on complexity. We recommend scheduling separate sessions for each exercise rather than attempting to complete multiple samples in a single interview. This prevents candidate fatigue and allows for more focused evaluation.

Should we allow candidates to use online resources during these exercises?

Yes, for most exercises. Professional engineers regularly consult documentation and resources when working. Allowing this creates a more realistic environment and focuses evaluation on problem-solving approach rather than memorization. The exception might be if you're specifically testing knowledge recall as a critical job requirement.

How should we evaluate candidates who don't complete the entire exercise?

Focus on the quality of what was completed rather than completion alone. Assess their approach, the clarity of their thinking, and how they prioritized work. A candidate who thoughtfully completes 70% of an exercise often demonstrates more valuable skills than one who rushes through 100% with lower quality.

Can these exercises be conducted remotely?

Absolutely. All these exercises can be adapted for remote interviews using collaborative coding platforms (like CoderPad or Replit), video conferencing with screen sharing, and collaborative diagramming tools (like Miro or Lucidchart). Ensure candidates have clear instructions for accessing these tools before the interview.

How do we ensure these exercises don't disadvantage candidates from underrepresented groups?

Design exercises that minimize reliance on specific cultural knowledge or contexts. Provide clear instructions and evaluation criteria. Allow candidates to ask clarifying questions. Consider offering a brief practice exercise to help candidates become comfortable with the format. Review your exercises regularly for potential bias and adjust based on feedback.

Should we share these exercises with candidates in advance?

For some exercises, particularly the system design and technical planning activities, providing the scenario in advance can lead to more thoughtful responses. For coding and debugging exercises, a general description of the format helps candidates prepare without compromising the assessment of real-time problem-solving skills.

The right backend engineer can transform your technology infrastructure, enabling your applications to scale reliably and perform efficiently. By incorporating these work samples into your hiring process, you'll gain deeper insights into candidates' capabilities than traditional interviews alone can provide. These exercises evaluate not just technical skills but also the problem-solving approaches, communication abilities, and collaborative mindset that distinguish truly exceptional engineers.

For more comprehensive hiring resources, check out our AI Job Description Generator, AI Interview Question Generator, and AI Interview Guide Generator. You can also explore our example job description for Backend Engineers for additional insights into defining this critical role.

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