CodeSubmit Interview Series

The 12 Best Blockchain Developer Interview Questions in 2023

Want to hire your next blockchain developer? Here, you’ll get the 12 best blockchain interview questions to ask at your next interview so that you can identify the right fit for your team. Read on!

Interviewing blockchain developers  

Blockchain developers have a key role in blockchain transactions by enabling secure digital transactions. They create systems to record and store blockchain data so that changes or hacks are prevented and design secure blockchain technologies, maintain client and server-side applications and develop application features and interfaces.

Blockchain developers naturally need to understand blockchain technologies and, depending on your needs, know different blockchains as building an application for one blockchain won’t be the same as for another. 

The languages they should know depending on your project, but some of the most popular programming languages for blockchain are C++, C#, JavaScript, Python, Ruby, and Java.

They also need to understand cryptography and security principles, as well as peer-to-peer networking and distributed systems. 

So, how do you identify developers with these skills? That’s what we’ll look at next. 

Beginner blockchain developer interview questions

What are the top junior blockchain developer interview questions? Here are the best questions to ask candidates who are in the early stages of their careers. These questions are all about understanding how well your candidates understand blockchain and the benefits and limitations of this technology. 

1. What is blockchain?


Blockchain is a secure, transparent, and incorruptible digital ledger that is used for economic transactions. It can be programmed to record virtually anything of value. Put simply, it’s a decentralized distributed database that isn’t owned by a single entity but is managed by a cluster of computers. It’s stored as a database or a flat-file. 

2. Explain how blockchain works. 


Blockchain is made of blocks or immutable records of data. These are linked with cryptography, a process to encrypt and secure data communication. Blockchain records the data, which won’t change once it’s been recorded, to avoid tampering with information.

3. What types of blockchains are there? 


There are three main types of blockchains. These are:

1) Public blockchain 

Anyone can read, write, and audit the blockchain. 

2) Private blockchain

Private blockchains are the property of individuals or organizations.

3) Consortium or Federated Blockchain 

Selected members can read, write, and audit the blockchain.

4. How do you identify a block?


Every block has four fields. These are: 

1) Details of transactions

2) Hash value of the previous block so that the blocks can be linked in the blockchain

3) Nonce, a random value that is used to vary the hash value to get a hash value, which is less than the target 

4) The digital signature of the block and an alphanumeric value used to identify the block (hash) 

5. What role does security policy play in blockchain?


Security policy is a plan to map out organizational objectives, procedures, and goals to ensure the security of blockchain from external threats. It also outlines situations where security threats can occur. 

Advanced blockchain developer interview questions

How do you interview senior blockchain developers? Here are the best blockchain developer questions for advanced candidates. 

6. What is the hash and how is it generated? 


The hash is a block signature that is generated by:

1) Passing transaction details using a one-way hash function.

2) Using the user’s private key to run the output value through a signature algorithm.

7. Explain fork and forking. 


Updating a cryptocurrency protocol or code is called forking and it means that a blockchain splits into two branches. This happens, for instance, if network participants can’t agree on the consensus algorithm and rules to validate transactions. There are three types of forking: hard forks, soft forks, and accidental forks. 

8. What are the steps to implement a blockchain project? 


The first step is to identify requirements. The process looks like this: 

1) Identify the problem and the end goal

2) Identify the most suitable platform 

3) Identify the most suitable consensus mechanism

4) Account for implementation and deployment costs

The next step is to plan the project to understand all the requirements and decide on the blockchain platform they’ll implement. 

The third step is to develop and implement a project. Here the steps are:

1) Design the architecture

2) Design the UI 

3) Build the APIs

And the final step is to control and monitor the project: 

1) Apply Proof of Concept 

2) Identify and fix problems 

9. What is secret sharing?


Secret sharing is a method for enabling data security in blockchain. It involves the segregation of personal or sensitive information into units. They are then sent to network users and the information is shared with participants who are allocated the share of the secret. 

10. What is the RSA algorithm? 


RSA stands for Rivest-Shamir-Adleman consensus algorithm. This algorithm is used for encryption and decryption of messages by leveraging modern computers. As it’s an asymmetric algorithm, it has two different keys, a public, and a private key. 

11. Describe how you handle risk management to secure transaction records? 


Risk management focuses on finding threats and vulnerabilities to the financial records of an organization and immediately acting on those risks.

12. Explain what nonce is and its role in mining.


Nonce is the number that is determined with proof of work. It’s a random value that’s used to vary the value of a hash so that the final hash meets the hash conditions.  

Proof of work is the process to validate transactions by solving a mathematical puzzle. Along with nonce, proof of work determines a cryptographic hash algorithm to produce a value that is lower than a predefined target. 

Over to you!

There you have it. These are the top blockchain developer interview questions. 

Related: The Best Ethereum Interview Questions

Interviews are one part of assessing your next blockchain developer. Assessment tests are another.

With our software assessment tests, you’ll quickly identify the right candidates.  

Try our blockchain development assessment tests here.