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Blockchain Developer interview questionsSmart Contract Coding Test round

A 60 min interview plan with a time-boxed script, what each question is for, and the signals to score against. Key skills: Smart Contracts, Coding, Solidity, Ethereum, Problem Solving.

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Introduction

5 min
•

Hi, I’m [YOUR_NAME], and I’m a [YOUR_TITLE] at [COMPANY_NAME]. I’m excited to learn more about your experience today.

•

Could you briefly introduce yourself and share what attracted you to apply for this position?

What this question is for, and what to listen for

Purpose

Assess communication skills, alignment with the role, and initial confidence.

Signals to score

  • Clear introduction provided
  • Relevant experience mentioned
  • Motivations for applying explained
  • Alignment with team values
  • Specific skills highlighted
  • Response is concise and organized
  • Understanding of role requirements

Follow-up questions

  • What excites you most about this position?
  • How does your background align with our team’s work?
•

Great, thank you for sharing! In the next 50 minutes, we’ll dive into a coding challenge focused on smart contracts. After that, you can ask any questions you have about the role or the company.

Smart Contract Coding Challenge

50 min
•

Develop a simple Ethereum smart contract for a decentralized voting system. Requirements: - The contract should allow users to register as voters. - Each voter can cast one vote for a candidate. - The contract should track the number of votes each candidate receives. - Implement a function to declare the winner based on the highest votes. Follow-Ups: - How would you handle security concerns in this contract? - What are the gas cost implications of your solution? - How would you test this smart contract?

What this question is for, and what to listen for

Purpose

Evaluate technical knowledge, problem-solving skills, and understanding of Solidity and Ethereum.

Signals to score

  • Clear understanding of smart contract requirements
  • Logical and structured approach
  • Explains thought process
  • Considers security and gas costs
  • Efficient, clean, well-formatted code
  • Tests and debugs the contract effectively
  • Open to feedback and adjusts accordingly

Follow-up questions

  • Can you explain your thought process on how to approach the problem?
  • How do you plan to handle security concerns in your solution?
  • Can you walk me through your code and explain each step?
  • How would you test your solution?
•

If you had more time, what would you change in your solution?

What this question is for, and what to listen for

Purpose

Assess the candidate's ability to reflect on their work, identify areas for improvement, and demonstrate critical thinking and problem-solving skills. A good answer should include specific suggestions for improvements or enhancements to the solution, such as optimizing performance, adding error handling, or addressing edge cases. The candidate should explain why these changes would be beneficial, showing their ability to think beyond the initial solution and consider its effectiveness and efficiency.

Signals to score

  • Recognizes limits in their original answer.
  • Points out clear areas to improve.
  • Suggests specific changes.
  • Talks about how changes could help performance.
  • Shares ideas clearly and logically.
  • Shows a desire to learn and improve.

Follow-up questions

  • What specific improvements would you make to enhance your solution?
  • How could you optimize the contract for better performance?
  • Are there any additional features you would consider adding?
•

Great job on the coding exercise!

Closing

5 min
•

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?
•

Thank you for your time today. We’ll be in touch soon regarding the next steps.

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Interview Template
Position
Blockchain Developer
Round
Smart Contract Coding Test for 60 min
Key skills
Smart Contracts, Coding, Solidity, Ethereum, Problem Solving

Blockchain Developer interviews — common questions

Who is this Blockchain Developer interview plan for?
It is written for the interviewer, not the candidate: the hiring manager, engineer or panel member running the Smart Contract Coding Test round for a Blockchain Developer role. It gives you a 60 min script to follow in the conversation — 4 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 Smart Contract Coding Test round assess?
This round is focused on: Smart Contracts, Coding, Solidity, Ethereum, Problem Solving. It works through Introduction, Smart Contract Coding Challenge and Closing, scoring against 28 observable signals, with follow-up prompts on all 4 questions for going deeper where an answer is thin.
How is the 60 min split up?
Introduction (5 min), Smart Contract Coding Challenge (50 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 Blockchain Developer?

A single round does not cover a whole role. The other rounds in this library for a Blockchain Developer: