15+ Blockchain Interview Questions and Answers for 2025

Blockchain industries are buzzing with innovation and technology. The market is expected to grow at a CAGR of 91.1% from 2023 to 2030. With a sector full of growth and opportunities, competition is steadily increasing. So, we have prepared a list of blockchain interview questions and answers to help you stay prepared and ace the interview round. Let us dive into it!  

Career Opportunities

Before diving into the questions and answers, let us explore the diverse career opportunities blockchain offers. 

• Blockchain developers: They are in demand as companies are looking for ways to implement blockchain into their operations.
• Blockchain UX Designer: They design user-friendly interfaces on a blockchain. 
• Blockchain Solution Architect: They leverage blockchain technologies to create and implement opportunities and solutions. 
• Blockchain Quality Engineers: They are professionals who make sure that all the blockchain operations are up-to-date and functioning. 

Beginner-Level Blockchain Interview Questions 

If you are a beginner in the industry, these blockchain interview questions will test your basic knowledge in the field. 

Q1. Explain Blockchain to someone who has no idea about it.

This question tests out your basic knowledge and understanding of blockchain. The interviewer expects you to provide an example, even a layman would understand. 

Ans: Let's start with an example. Imagine your university provides a digital version of your mark sheet. Whenever results are out, they update it on a blockchain, to which you also have access. All your semester mark sheets are stored there in chronological order. 

If the university updates any marks or grades, you will be able to view them in real time. Since the blockchain network is decentralised, your university does not have full authority over the data. Everyone else can view it and verify the validity of the data. 

Q2. What are some blockchain platforms to build applications?

This question tests your practical knowledge about the industry.

Ans: Popular blockchain platforms are:

1. IBM Blockchain
2. Hyperledger Fabric
3. Stellar
4. Ripple
5. Hyperledger Sawtooth

Q3. What do you understand about the Merkle Tree?

It is a technical question testing your basic depth of knowledge. 

Ans: A Merkle Tree is a way of verifying data in a blockchain. It is a tree-shaped binary code containing a cryptographic hash. These hashes verify the data. 

Q4. How will you identify a block in a blockchain?

This question wants to know the components of a block. 

Ans: Every block in a blockchain contains four elements. They are:

1. Hash value of the previous block.
2. Transactional data.
3. A nonce.
4. Hash of the current block.

Q5. Suppose the data present in a blockchain is wrong, and a company asks you to modify it. What will you do?

Interviewers ask this blockchain interview question to assess your core understanding of how blockchain functions.

Ans: In such a situation, all data in the blockchain has to be deleted. Therefore, it is impossible to change any data once added to the blockchain. Companies have to exercise excessive scrutiny and diligence when working with blockchain. 

Q6. What is cryptography?

Ans: In the blockchain, cryptography ensures transparency and security. Cryptography encrypts and decrypts transactional data in a blockchain. 

Q7. Explain a genesis block.

Ans: The first block in a blockchain is called a genesis block. 

Q8. What is a public key?

Ans: A public key, used by everyone, is a way of sharing encrypted data with the recipient. The encryption is done in such a way that the message can only be decrypted using another key, called a private key. 

Q9. Mention a real-world use case of blockchain.

Ans: Google is a great example of real-life use cases of blockchain. The tech giant provides Blockchain Node Engine, allowing users to manage blockchain nodes and deploy smart contracts. 

Q10. What are dApps?

Ans: dApps or decentralised applications are blockchain-based applications where a single entity does not control the functioning of the app. It works on a peer-to-peer system. 

Also Read:- Unlocking Your Future: Top Career Paths After a Blockchain Master’s Degree

Intermediate-Level Blockchain Interview Questions

Now that the basic questions are out of the way, let us look into intermediate blockchain interview questions. 

Q1. What algorithm does Bitcoin use? Also, list other cryptographic algorithms.

Interviewers expect you to list at least 5 algorithms, along with Bitcoin’s. 

Ans: Bitcoin uses the SHA-256 algorithm. Other popular algorithms are:

• Triple DES
• Blowfish
• RSA
• Ethash

Q2. How do you plan to handle the risks of securing transaction records? 

This question is often asked in blockchain developer interviews. It assesses your practical knowledge and problem-solving skills in the field of blockchain.

Ans: I would identify possible financial vulnerabilities and risks of a company and take countermeasures as soon as possible. This will help me in the event of data loss or tampering. 

Q3. What challenges have you faced while developing blockchain applications?

The interviewer is trying to see whether or not you acknowledge common challenges blockchain developers face. Provide a solution for every problem you state. 

Ans: Challenges include:

• Securing a network.
• Creating a bug-free and tamper-proof smart contract.
• Ensuring transaction privacy. 

By implementing strong encryption and developing a risk and threat model, blockchain networks can be secured. To create a bug-free smart contract, Solidity IDE works the best. Transaction privacy is best handled with Zero Knowledge Proofs, Blind Signatures and Ring Signatures. 

Q4. Give some examples of Blind Signatures.

Further testing your knowledge, this blockchain interview question is straightforward and to the point. 

Ans: The most common examples are EVS (Electronic Voting System) and digital cash schemes. 

Q5. What do you specify in a Solidity file at the beginning?

Since Solidity is the most convenient language for blockchain development, this question is often asked. 

Ans: Version Number must be specified before beginning the code. 

Blockchain Interview Questions: Advanced Level

Certain situation-based questions fall under the advanced job role umbrella. Moreover, at this level, interviewers dive deep into the technicalities of blockchain. 

Q1. On what factors does gas usage in transactions depend? Also, how is the transaction fee calculated?

This blockchain interview question aims to check whether you have experience managing transactions.

Ans: It depends on the storage amount and the code of a smart contract. The ‘Tx = Gas price * Gas Limit’ formula calculates the transaction fee. 

Q2. How will you stop double-spending?

Further diving deep, interviewers are testing your practical problem-solving skills in blockchain. 

Ans: Double-spending can be tackled with Proof-of-Work consensus mechanisms and cryptographic encryptions. However, blockchain networks still face an issue of 51% of attacks. 

Q3. What is a 51% attack? 

Ans: A 51% attack refers to a group of malicious black-hat hackers trying to gain control over more than 51% of the network's hashing power. This gives them the power to reverse transactions and double-spend. 

Q4. Explain how the Ethereum Virtual Machine works.

Ans: The EVM is a state machine that allows the Ethereum blockchain to interpret and execute a smart contract. It also allows developers to create custom non-fungible tokens and currencies. 

Q5. What do you mean by function modifiers in Solidity?

Ans: To change how a smart contract works, function modifiers are used. With them, developers can build custom features, and additional logic, and apply restrictions. 

Conclusion 

These blockchain interview questions and answers help you showcase your expertise in the technology and secure your dream job. Do you want to step into the amazing world of blockchain? Amity Online University offers an online blockchain course, positioning you in the industry. Coupled with these blockchain developer questions, you are sure to make an impact in the growing field. So, what are you waiting for? Enroll today!