Top 50 Blockchain Interview Questions and Answers


Blockchain technology has surfaced as one of the quickest growing technology with numerous renowned companies offering myriads of options for qualified individuals. Hence, developing a career in Blockchain will offer you an excellent and rewarding prospect. 

An interview is another crucial stage of landing a job in Blockchain technology. Blockchain interview questions can be tricky and for beginners, it might be a difficult stage to crack through. To help you ace your next interview, the following set of top blockchain interview questions is compiled taking careful consideration.

These blockchain interview questions will assist you in preparing and enabling you to successfully complete the interview. You will be asked many questions on blockchain as a candidate. There are several levels of difficulty associated with each of these questions. We have categorized these blockchain interview questions and answers into varied levels. You can prepare well and engage with the answers fully by using these top blockchain interview questions. 

Blockchain Interview Questions and Answers for Basic Level

1. Define Blockchain Technology.

The blockchain is a decentralized, irreproachable digital database of economic activity that may be used to record nearly any exchange of value, not just money.

2. Explain a Blockchain wallet and its method of working.

A blockchain wallet is a piece of computer software that keeps track of and logs all transactions involving private and public keys on the blockchain. Theoretically, a blockchain wallet does not hold bitcoin; instead, all information pertaining to these keys is kept on the blockchain that the wallet is hosted.

Public and private keys are used in blockchain wallets. In blockchain wallets, both a public key and a private key are utilized similarly. In that it can be distributed to others, a public key is like an email address. A public key is generated when your wallet is created, and you can share it with others to collect funds. A public key is also generated when your wallet is created, which you can use to share money with other people. The private key must be kept a secret at all times. It should not be hacked and you shouldn't reveal it, just like your password.

3. Explain in brief about Ethereum. 

Ethereum is a blockchain-based open-source software platform that allows programmers to create and distribute decentralized apps (i.e., applications that are not controlled by a single entity). You might create a decentralized application where decisions are made by the users themselves.

4. What distinguishes the Ethereum and Bitcoin blockchains?

The Ethereum blockchain is very different from the bitcoin blockchain, despite the fact that both bitcoin and ether are digital currencies. Bitcoin was developed specifically to function as a digital currency. While the blockchain technology used by Ethereum is more comprehensive. Organizations are also embracing distributed ledger technology to develop new services, although Ethereum is far more reliable than bitcoin.

5. Explain Smart Contracts function and how they function. 

A smart contract is a two-party contract that is built on computer code. They operate on the blockchain and are kept on a public ledger where they cannot be altered. The blockchain handles transactions for smart contracts, allowing for automatic submission of those transactions without the need for a middleman. Smart contracts are accurate, autonomous, secure, and free of third parties.

6. Explain Cryptocurrency and the working of Bitcoin Mining

The practice of obtaining cryptocurrency through the use of computers to solve cryptographic equations is known as "crypto mining." This method also includes validating data blocks and applying transaction records to a public record (ledger).

In addition to creating new bitcoins, the process of mining bitcoins is crucial for maintaining and expanding the blockchain ledger. It is performed with the aid of exceedingly sophisticated computers that resolve incredibly challenging computational arithmetic problems.

7. Define a Blockchain Explorer

A blockchain explorer is a piece of software that combines an API and a blockchain node to extract data from a blockchain. It then organizes the data using a database and displays it to the user in a searchable fashion.

8. What is Hashing?

In the blockchain, hashing refers to the act of turning an input item of arbitrary length into an output item of a specific length. Consider the blockchain's application to cryptocurrencies, where transactions of various duration are processed using a single hashing method to create a fixed-length performance for each.

9. Can you list the various Blockchain Types?

The Blockchain can be categorized in the following variants:

  • Public Blockchains
  • Private Blockchains
  • Consortium Blockchains
  • Hybrid Blockchains.

10. What advantages does blockchain technology offer?

The advantages of blockchain technology are as follows:

  • Compared to previous networks or record-keeping systems, blockchain technology uses superior security. All transactions must be approved before being recorded. After being authorized, a transaction is encrypted and linked to the prior transaction.
  • Transparency is offered via blockchain. Transparency is a significant issue in the new industry. A company may use blockchain to build a wholly decentralized network that does away with the need for a centralized authority, enhancing the transparency of the system.
  • Blockchain aids in cost reduction. By adopting the blockchain instead of paying third-party providers, businesses can save a lot of money.
  • Blockchain streamlines laborious procedures to improve efficiency. It also gets rid of human errors using automation. Blockchain thus boosts productivity and speed.
  • The blockchain enables instantaneous traceability. Fraud is avoided because it creates an audit trail that documents an asset's provenance at each step of its travel.

11. Can you state some of the popular Blockchain Platforms?

some of the majorly popular platforms that utilize Blockchain-based applications are: 

  • IBM Blockchain
  • EOS
  • OpenLedger
  • Corda
  • Ripple
  • Ethereum
  • IOTA
  • Quorum
  • OpenChain
  • Hyperledger Sawtooth

12. What distinguishes Hyperledger from Blockchain?

With the help of blockchain technology, we can create decentralized systems. When we examine blockchain, the "block" stands for information that is saved in a digital format, and the "chain" stands for the database that contains that information.

One kind of blockchain platform is Hyperledger. It is an open-source blockchain network. Each of these blockchains has its own storage practices, consensus, smart contracts, identification, and access management systems.

They share some features since hyperledger is a byproduct of the blockchain platform. Both are distinct, nevertheless, because of the peculiar properties of hyperledger. Generally speaking, there are two sorts of blockchain- public and private. A private blockchain example is Hyperledger.

13. Name some popular Cryptocurrencies.

Some of the most favorable and preferred  Cryptocurrencies are:

  • Bitcoin(BTC)
  • Ethereum(ETH)
  • Ripple(XRP)
  • Litecoin(LTC)
  • Bitcoin Cash(BCH)

14. Describe a ledger. What distinguishes a distributed ledger from a conventional ledger?

A ledger is a developing document. It keeps an archive of every exchange between two parties on the blockchain network. A distributed ledger is a digital data repository that is copied, traded, and synchronized among several locations over a network. Contrary to traditional ledgers (think banks, governments, and accountants), distributed ledgers offer a network of synchronized databases with an auditable history of information that is available to all users.

15. How does a 51% Attack work?

A 51 percent attack on a blockchain network refers to an attempt by a miner or group of miners to take over more than 50% of the network's hashing capacity, processing power, or hash rate. In this attack, the attacker may stop new transactions from occurring or being validated. While in control of the network, they can also undo transactions that have already been verified, creating a double-spending issue.

16. How will you differentiate between Blockchain and Relational Database?

Let us consider the following points to compare Relational Database with Blockchain:

Blockchain has a block as a unit of data while a relational database has a table. 

With blockchain, there is no single point of failure while there is in the case of RDBMS. 

In the blockchain, there is no centralized control while it is present in RDBMS.

While editing is possible in RDBMS, no editing or deleting is possible with Blockchain. 

17. What are the blocks regarding block technology?

A block in the Blockchain is just a collection of records. The procedure of connecting these lists together is referred to as a "Blockchain". A block is referred to as each ledger book of a company's  100 ledger books, which together make up the blockchain. 

18. How does the Blockchain approach identify a block?

Any block in this online ledger basically consists of transaction information, a time stamp, and a hash pointer that connects it to the preceding block.

19. Are there any requirements for implementing Blockchain technology in a network specifically?

No, using it is not subject to such limitations. The network must be a peer-to-peer network, nonetheless, according to the concerned protocols. Without relying on outside apps, it successfully validates the new block and helps businesses stay up with the speed in this sector.

20. Can data be changed after it has been written in a block?

The answer is no, you cannot do that. The business only needs to remove the details from all other blocks if any change is required. When using this technique, data must be handled extremely carefully if for no other reason.

21. What kinds of records are compatible with the blockchain? Are there any limitations?

The quantity of records that can be held in the Blockchain techniques is not constrained. It's crucial to bear in mind that record keeping is not just for these programs. 

Some instances of the kinds of information that can be stored on them include the following:

  • Records of health transactions
  • Identity Management
  • Transaction productions
  • Organizational activities and managerial duties
  • Need for documentation

22. How do blocks get created in a Blockchain?

The blockchain automatically generates blocks once the block size is achieved. The transactions are saved up until the file is finished because the block is a file. The most recent block is connected to the one before it. To identify a block, a mathematical procedure generates a hash value. Additionally, it displays any changes made to a block.  

23. Are Blocks from a Blockchain Removable by Anyone?

The way blocks are handled completely determines how they are erased from a blockchain. Block removal cannot be done manually. However, if it is destroyed, the blockchain might try to reconstruct the database using other peers.

Since they don't require ongoing maintenance, they can be eliminated once they've been examined in order to lower the size of the blockchain. If necessary, you can download it again. Pruning is the name of this process.

24. Describe encryption. What part does it play in Blockchain?

Data security is achieved through the use of encryption. In this method, the sender encrypts the data to some extent before sending it outside of a network. It will only be able to be decoded by the receiver. This strategy works well with blockchain since it simply increases the overall security and reliability of blocks, increasing their stability.

25. Can you explain briefly about security in the block?

A block cannot be modified by any users on the network. It provides a high level of security as a result. Additionally, each block is encrypted to ensure its security, which is another vote in this situation. Therefore, there is no requirement for concern regarding data protection in a block.

26. Why is the blockchain a reliable method?

Blockchain is reliable for a wide range of uses. The first thing that springs to mind when thinking about its open-source nature is its compatibility with various commercial software. Its safety is the second consideration. The developers took extra attention to staying up to date with protection because it was intended to be used for online transactions. Regardless of the matter, the type of firm one owns, blockchain will be helpful.

27. How Does Secret Sharing Work? Does it improve blockchain technology in any way?

It goes without saying that security is crucial in digital transactions. Secret sharing is a technique used in Blockchain technology to break down private or confidential information into manageable chunks and deliver them to network users. A person who has been given a share of the secret must decide to combine the original knowledge with others in order for it to be done. There are a variety of security advantages to using blockchain technology.

28. What do Blockchain robustness and durability mean?

The track record of Bitcoin has become highly encouraging for blockchain technology which will continue even in the future. Bitcoin came about in 2008 and has sustained no significant harm since then. The internet has shown to be a trustworthy resource for almost 30 years. Similar to how the internet has resilience built in, so does blockchain technology. Since the blocks of information stored in the blockchain are identical across its network, it cannot be governed by a single person. The blockchain shouldn't have a single point of failure.

29. How is blockchain used by Bitcoin?

A transaction is a value transfer between Bitcoin wallets that are documented in the blockchain. Private keys often referred to as seeds, are kept in bitcoin wallets and are used to sign transactions and demonstrate mathematically that they originated from the wallet's owner.

30. Is the blockchain a trustworthy ledger?

Blockchain is an irreproachable ledger, yes. The blockchain database cannot be tampered with, claims the inventor.

31. What are the conditions for a blockchain?

Blockchain is a technology that has the power to completely alter corporate networks. Therefore, the following are the prerequisites for a blockchain:

  • Smart contracts
  • Ledgers
  • Cryptography
  • Consensus Protocol

32. What sequence does the blockchain's chain of blocks follow?

The blockchain links every block in reverse order at all times. Or to put it another way, a blockchain links every block to every other block. As a result, blocks are connected in reverse.

That's about it regarding top Blockchain interview questions for beginners.  Let us proceed to the next level of Intermediate/mid-level  Blockchain interview questions in the following section.

Intermediate-level Blockchain Interview Questions and Answer

33. Explain Block Identifiers.

Each block in a blockchain has a special identification number.  To produce a distinctive identification, the hash value is employed. No two block identification would be similar consequently. Blocks in blockchain can be recognized by their block height and block header hash. 

34. What are some popular types of ledgers that users of blockchain technology can take into account?

Users of the blockchain can take into account one of three popular forms of ledgers:

  • Centralized Network
  • Decentralized Network
  • Distributed Network

35. What distinguishes a blockchain ledger from a traditional ledger?

The fact that a blockchain is a distributed database that can be easily decentralized is the main contrast between a blockchain ledger and a traditional ledger. Compared to a typical ledger, this system has a far lower probability of error. Ordinary ledgers are produced manually or through human effort, however, the Blockchain has all of its procedures automated. All that's left to do is set it up correctly and in accordance with the directions.

36. What is double spending, exactly? In a blockchain system, is it possible to double spend?

Since the token is often composed of a digital file that is simple to copy, it happens when a single digital token is utilized many times. Simply put, it promotes inflation and forces firms to take a big loss. The elimination of this procedure as much as feasible is one of the key objectives of blockchain technology.

By requiring many parties to validate a transaction before it is added to the ledger, the blockchain prevents double-spending. It's not hyperbole to say that the entire design of bitcoin, including the Blockchain, mining, proof of work, complexity, and other features, is intended to produce a transaction history that is computationally impossible to alter.

37. What does blind signature mean and how is it helpful?

In a blind signature, the contents of the message are concealed (blinded) before the signature is made. The resulting blind signature can be publicly authenticated against the original, unblinded message, just like a regular digital signature.

In privacy-related protocols, blind signatures are frequently used when the signer and message author are different people. Digital cash systems and cryptographic voting systems are two examples.

38. What exactly is an off-chain transaction?

Off-chain transactions are transactions that happen away from the blockchain. An off-chain transaction records and validates the transaction using different techniques, whereas an on-chain transaction, which is frequently referred to as simply "a transaction," changes the blockchain and depends on it to demonstrate its legality.

39. How will you handle risk management when it comes to protecting the transaction records?

In essence, risk management is a process for identifying all threats to a company's financial information. The best course of action with this tactic is to implement the necessary defenses as soon as possible.

Another choice is to have a backup plan in place. Based on the value of knowledge, further approaches, such as buying new risk management technologies, may be taken into consideration. The threat from black-hat hackers to data is the greatest.

40. What risks exist for the knowledge you are familiar with?

The hazards to knowledge are considerable in the contemporary context. As a result of the increase in online transactions, many hackers have joined in and are introducing new tactics to hack information and servers that handle financial information.

Major hazards include sabotage, identity theft, data extortion, and software attacks. There are also worms, Trojan horses, and other harmful software.

41. What Sets Proof-Of-Stake (Pos) and Proof-Of-Work (Pow) Apart?

The two most often used consensus algorithms, PoW and PoS, can be distinguished based on how they work. 

PoS does not require as many resources as PoW does. 

Other notable distinctions include the requirement for a large amount of computing power in PoW as opposed to none or very little in PoS. 

In comparison to PoW, PoS is more economical and completes tasks faster.

42. What are the fundamental principles required to eliminate security threats in Blockchain?

The essential Guidelines that must be followed to reduce security threats are listed below. These ideas are quite basic and easy to put into practice. They aid in increasing the value of transactional papers.

  • Auditing
  • Securing applications
  • Securing testing and similar approaches
  • Database security
  • Continuity planning
  • Digital workforce training

43. Give names of the most popular consensus algorithms

Some of the most well-known consensus algorithms are:

  • PBFT (Practical Byzantine Fault Tolerance)
  • Proof-of-work
  • Proof-of-stake
  • Delegated proof-of-stake
  • Proof-of-elapsed time

44. What are the steps involved in the implementation of the Blockchain Project?

There are six steps that are essential for implementing a blockchain project as follows:

  • Determining the requirements 
  • Conceptual consideration for screens
  • production of a blockchain project
  • Feasibility Study of Security Implementation
  • Directing and coordinating the project

45. Define a Public key.

A Public key is used in the cryptographic technique that allows peers on a blockchain to access the money in their wallets. When a public key and a private key are linked together, a pair of leys is produced. The private-public key pair is used to make sure that the security of the blockchain is upheld. An address or node's unique set of alphanumeric characters is known as a public key. 

46. Define a Private Key 

A private key is used to encrypt data connected with a public key which is also an alphanumeric phrase. It is also a part of the cryptographic techniques used to secure blockchains. Only the key generator is authorized to use the key, which has been assigned to him. If he doesn't, someone else may be able to access the wallet's contents, including the address where the private key is kept.

47. Elucidate briefly on the loopholes and limitations of Blockchain.

The following are some of the demerits of Blockchain technology:

  • Because blockchain isn't a distributed computing system, some blockchain solutions consume a lot of energy.
  • Complex technology integration and management are challenging.
  • Scalability is a challenge as well.
  • Data cannot be altered.
  • Because of the varying network speed and transaction costs, it can occasionally be inefficient.
  • Human mistake is still a problem today.
  • Not completely safe


Let us now move on to the next level of the blockchain  interview questions

Advanced-Level Blockchain Interview Questions and Answers

48. How can Double-Spending be prevented?

Blockchain prevents double spending with its consensus method. Before adding the transaction to the block, the consensus algorithm confirms its validity. It is therefore verified by a number of nodes, enabling double-spending.

49. Define Consensus Algorithm.

A consensus algorithm is a technique for reaching an agreement on a modification to data across a system or any distributed network. They are frequently utilized in blockchains as a result of their ability to let the network of unidentified nodes come to an agreement on the data that is being exchanged or stored. Among consensus algorithms, Proof-of-Stake (PoS) and Proof-of-Work (PoW) are most widely used.

50. What does "Coinbase transaction" mean?

A Coinbase transaction is the first transaction in a block. This distinct form of bitcoin transaction will be created by a miner. The block reward for their work, as well as any other transaction fees, are paid to miners using it. However, a 51% network attack will make any blockchain susceptible to double-spending because more than 50% of the network is owned by one party.

That brings us to the conclusion of the top Blockchain interview questions and answers which have been created for aspiring professionals to crack the interview in their first attempt and fetch a job in blockchain technology. 


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