Explain what a blockchain is to someone who is not technical.
What the interviewer wants to hear
- Shared ledger copied across many computers
- Blocks linked by cryptographic hashes make history tamper-evident
- Consensus decides which transactions are added
- No single owner; rules enforced by code
- Gives a simple real-world example
Model answer
A blockchain is like a shared notebook of transactions that thousands of computers around the world keep identical copies of. Every few seconds, a new page, called a block, is added with a batch of transactions. Each page includes a fingerprint, called a hash, of the previous page, so if someone tries to change an old entry, all later fingerprints stop matching and everyone can see the tampering. The computers follow a set of rules, called consensus, to agree on which new page is valid; Ethereum uses proof of stake, where validators lock up ETH and lose some if they cheat. Because no single company owns the notebook, people who do not trust each other can still agree on who owns what. Smart contracts are small programs stored in this notebook that run automatically, like a vending machine that pays out when conditions are met.
Can you answer it under time pressure?
Take a timed easy round and get scored on every answer.
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