Blockchain Interview Questions And Answers

Blockchain Interview Questions And Answers

As blockchain technology develops, now is the perfect time to join as a developer. In this article, we focus on standard blockchain interview questions that are common during blockchain developer interviews. Suppose you planning to start a blockchain career.

1. What is Blockchain?

A blockchain is a sort of distributed ledger. DLT, or distributed ledger technology, allows records to be shared among several computers or "nodes." A node can be any blockchain user, but it requires a lot of computer power to run. Nodes store data in the ledger and check, authorize, and save it. This differs from traditional record-keeping methods, which save data in a single area, such as a computer server. A blockchain splits freshly supplied data into blocks or collections of data. Because each block contains a particular amount of data, new blocks are constantly added to the ledger, building a chain.

2. What are blockchain blocks?

Blocks are data structures present in the blockchain database that are used to permanently record transaction data. A block contains all of the network transactions. After the data in the block has been authenticated and chained to the blockchain, the block is closed. Then, a new block is created to validate more transactions and add to the blockchain.

3. What are the key features of blockchain?

The key features of blockchain include.

  • Decentralization: The movement of power and authority from a centralized entity (an individual, an organization, or a group) to a distributed network is referred to as decentralization.
  • Immutability: Once a transaction is added to the ledger, it cannot be modified by another participant.
  • Greater Security: Because blockchain operates on a distributed network of nodes, data is always circulated among several nodes, guaranteeing that the integrity of the original data is not jeopardized.
  • Consensus: The consensus algorithm is what makes blockchain technology so effective. It is a decision-making mechanism for the network's active nodes (based on majority rules).

4. What is blockchain mining?

Blockchain mining is the process of adding new transactions to a blockchain's distributed ledger of existing transactions. Mining entails creating a hash of a block of transactions that is impossible to tamper with while preserving the integrity of the entire blockchain without the use of a central system.

5. What Are Private Keys?

To protect an address, private keys are utilized. Anyone who has it passes ownership to the person who holds it. Thus, the owner should keep it secure. Bitcoin keys, in particular, contain a 256-bit string consisting of letters and integers. It is stored in your cryptocurrency wallet, where you can access your Bitcoin whenever you want.

6. What encryption algorithm is used by the Bitcoin Blockchain?

Different blockchains employ a variety of encryption techniques. The SHA256 Hashing algorithm is used on the Bitcoin Blockchain.

7. How many users modify data in blockchain?

Users are unable to change data that has already been stored in the blockchain. Existing entries can't be changed or deleted. This helps to avoid data manipulation.

8. What is the role of coins or tokens in blockchain?

Tokens or coins are used as a medium of exchange by the states. They are digital assets that are embedded into a blockchain to perform a specific activity. When someone makes a transaction, coins are transferred from one address to another, changing their status. Furthermore, transactions contain some extra data that can be modified when a state changes. As a result, blockchains need money or tokens to entice users to join their networks.

9. What exactly is a public key?

A public key, unlike a private key, is intended to be shared with others so that they can transfer your Bitcoin. It is linked to the owner's private key, which is needed to "unlock" the public key. Bitcoin addresses are occasionally used for transactions instead of public keys because they are effectively compressed versions of the public key.

10. What separates a dApp from an app?

Apps aren't often designed to work in a decentralized environment. However, dApps run on a decentralized network or system. dApps are next-generation applications that are built on blockchain technology. NEO and Ethereum are two well-known blockchain platforms that support decentralized applications (dApps).

11. What is Bitcoin?

A bitcoin is a type of digital currency that can be bought, traded, and exchanged between two people safely through the internet. It can be traded electronically despite the fact that it cannot be touched or seen. We can save it as a virtual currency in our phones, PCs, or any other storage medium.

12. What is Mempool?

The mempool serves as a repository for unmined blockchain transactions. Although these transactions have been validated, they have yet to be published on the blockchain. The term "mempool" is a combination of the words "memory" and "pool," and it refers to a node's storage area where validated transactions are stored until they are mined and added to the blockchain.

13. What is EVM?

The term EVM stands for Ethereum Virtual Machine. It is a decentralized virtual computer capable of running scripts on the public node network. It's also Turing complete, with Gas acting as a pricing system within.

14. What do you mean by "Bitcoin Mining"?

Bitcoin mining is analogous to gold mining. Specialized computers capable of solving algorithmic equations are required for the procedure. This equipment lets miners authenticate blocks of transactions stored within each network. Miners that confirm and authenticate blockchain transactions are compensated in Bitcoin. These miners have the ability to create new coins, which will continue until the last Bitcoin is discovered.

15. Explain smart contract use cases.

Smart contracts are self-executing agreements with predefined rules and conditions, often deployed on blockchain platforms. They have diverse use cases, including automating financial transactions, such as lending and trading; managing supply chain processes; enabling decentralized applications (DApps); ensuring transparent voting systems; and facilitating secure, trustless interactions in various industries like real estate, insurance, and healthcare. Smart contracts enhance efficiency, transparency, and security while reducing the need for intermediaries in these applications.

16. What is Ethereum?

Ethereum is a blockchain-based software platform on which developers can create and deploy decentralized applications. It, like Bitcoin, is a distributed public blockchain network. Users on the Ethereum blockchain work to acquire Ether, a form of crypto asset that powers the network.

17. Explain different types of blockchain networks.

There are different types of blockchain networks.

1. Public blockchain networks
A public blockchain, such as the one utilized by Bitcoin, is one that anybody may join and use. One of the potential drawbacks is

  • The requirement for a lot of processing power.
  • A lack of transaction privacy.
  • Weak security.

2. Private blockchain networks
A private blockchain network is akin to a decentralized peer-to-peer network. However, a single entity controls the network's governance, conducting a consensus mechanism and managing the shared ledger.

3. Permissioned blockchain networks
Businesses that construct a private blockchain often create an authorized network. As a result, there are restrictions on which transactions and who can participate in the network.

4. Consortium blockchains
Multiple organizations may maintain a blockchain. Who may submit transactions and access the data is determined by these pre-selected organizations.

18. What is 51% Attack?

All transactional data is stored in the blockchain, which is a chain of blocks, throughout a given time period. The block cannot be changed once it is in the system, and users of the network would immediately reject the bogus data. The recording of new blocks, however, can be hampered if 51% of the miners are under the control of an attacker group. They can halt transactions made by other users and also turn them around. As double spending, it has additional names. Doubling up on purchases might cause a network to lose trust. A 51% attack is what is then known as this type of attack.

19. How are blocks identified?

The block height and block header hash are used to identify blocks.

20. What is the difference between Proof of Work and Proof of Stake?

The following are the main differences between Proof of Work and Proof of Stake:

Proof of Work

The Proof of Work (PoW) technique is used to validate the transaction and add another block to the chain. Miners compete against each other to finish the transaction on the network with this algorithm. Mining refers to the process of competing against one another. It describes a costly computer calculation. The first miner to solve each block's problem is rewarded.

Proof of Stake

In the case of the PoS algorithm, a group of nodes decides to stake their own currency for transaction validation. They are referred to as ' stakers.' In proof of stake, the author of a new block is chosen in a deterministic manner based on its wealth, which is also defined as stake. It does not provide a block reward. Therefore, miners just receive transaction fees. Proof-of-Stake can be thousands of times more cost-effective than proof-of-work.


Blockchain technology is a rapidly evolving field with diverse applications across industries. Understanding its fundamentals, use cases, and challenges is crucial for success in blockchain-related roles. These interview questions and answers provide a starting point for your preparation.