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Blockchain

50 Blockchain interview questions

Only coding challenges
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Blockchain Fundamentals


  • 1.

    Can you explain what a blockchain is and how it works?

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  • 2.

    What is the difference between a public blockchain and a private blockchain?

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  • 3.

    What are the key features of a blockchain that make it secure?

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  • 4.

    How does a blockchain ensure data integrity and prevent tampering?

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  • 5.

    Can you explain the concept of decentralization in blockchain?

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  • 6.

    What is a consensus mechanism, and why is it important in blockchain technology?

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  • 7.

    Describe the most common types of consensus algorithms and how they differ.

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  • 8.

    How does a blockchain achieve consensus in a distributed environment?

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  • 9.

    What is a node in the blockchain context, and what role does it play?

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  • 10.

    Can you explain what a blockchain fork is and why it might occur?

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Cryptography in Blockchain


  • 11.

    How does cryptography secure transactions and blocks in a blockchain?

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  • 12.

    What is a hash function, and why is it crucial to blockchain technology?

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  • 13.

    Can you explain asymmetric encryption and how it’s used in blockchains?

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  • 14.

    What is a digital signature, and how does it provide authenticity in transactions?

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  • 15.

    How do public and private keys work within blockchain?

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Smart Contracts


  • 16.

    Define smart contracts and how they operate within a blockchain.

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  • 17.

    What platforms can you use to deploy smart contracts, and what are their differences?

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  • 18.

    How can smart contracts access off-chain data?

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  • 19.

    Explain how smart contracts handle exceptions or errors.

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  • 20.

    Can you describe a potential security vulnerability in a smart contract?

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Ethereum Basics


  • 21.

    What is Ethereum, and how does it differ from Bitcoin?

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  • 22.

    Can you describe what Gas is in the context of Ethereum?

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  • 23.

    What is the Ethereum Virtual Machine (EVM), and what is its role?

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  • 24.

    How is the state of the Ethereum blockchain maintained?

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  • 25.

    Explain what ERC-20 and ERC-721 tokens are.

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Blockchain Data Structures & Design


  • 26.

    Explain the structure of a blockchain block and its contents.

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  • 27.

    What is a Merkle tree, and why is it important in blockchain?

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  • 28.

    How can blockchain systems ensure scalability and performance?

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  • 29.

    Describe the process of adding a new block to a blockchain.

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  • 30.

    What considerations are involved in designing a blockchain architecture?

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Transactions and UTXOs


  • 31.

    Explain the concept of transactions within a blockchain.

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  • 32.

    What is a UTXO, and how is it different from an account/balance model?

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  • 33.

    How are fees determined in a blockchain transaction?

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  • 34.

    Describe the lifecycle of a blockchain transaction from creation to confirmation.

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  • 35.

    What is a mempool in the context of blockchain?

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Blockchain Security


  • 36.

    Discuss the concept of the 51% attack and its implications.

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  • 37.

    How can a blockchain prevent double-spending?

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  • 38.

    What are some common security threats to blockchain systems?

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  • 39.

    Can you explain how blockchain immutability is maintained?

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  • 40.

    How does a blockchain network defend against Sybil attacks?

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Interoperability and Scalability


  • 41.

    What strategies exist to improve blockchain scalability?

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  • 42.

    How can different blockchain networks achieve interoperability?

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  • 43.

    Explain the concept of sidechains and how they work.

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  • 44.

    What role do layer 2 protocols play in blockchain?

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  • 45.

    Discuss the trade-offs between scalability, security, and decentralization.

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Blockchain Development and Testing


  • 46.

    What tools and environments are available for blockchain development?

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  • 47.

    How would you approach testing smart contracts?

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  • 48.

    What is a testnet, and why is it important for blockchain developers?

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  • 49.

    Can you explain the difference between on-chain and off-chain coding?

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  • 50.

    How can you ensure that a blockchain application is GDPR compliant, considering the immutability of data?

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