Web3 & Blockchain Interview Questions

calendarDec 14, 2025 · 2 min read · web3 blockchain ethereum solidity defi smart-contracts  ·
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Comprehensive Web3 and blockchain interview questions covering Ethereum, Solidity, DeFi, security, and advanced protocol design.

Blockchain Fundamentals

Core concepts every Web3 developer should know:

  • Easy: Blockchain basics, Ethereum vs Bitcoin, smart contracts, gas, wallets, keys, ERC-20, NFTs, dApps, Web3.js/Ethers.js, IPFS
  • Medium: DeFi protocols, advanced Solidity, reentrancy, proxy patterns, oracles, Layer 2, EIP-1559, signatures, flash loans, vulnerabilities
  • Hard: MEV, zero-knowledge proofs, complex DeFi, cross-chain bridges, governance, Diamond pattern, account abstraction, concentrated liquidity, DID, treasury management

Smart Contract Development

  • Solidity: Syntax, data types, modifiers, visibility, inheritance
  • Security: Reentrancy, overflow, access control, front-running
  • Patterns: Proxy, factory, diamond, pull-over-push
  • Testing: Hardhat, Foundry, unit tests, integration tests
  • Gas Optimization: Storage patterns, calldata, packing

DeFi Protocols

  • DEX: AMM, Uniswap, concentrated liquidity
  • Lending: Aave, Compound, liquidations
  • Stablecoins: DAI, USDC, algorithmic stablecoins
  • Yield Farming: Liquidity mining, staking
  • Flash Loans: Arbitrage, collateral swaps

Consensus Algorithms

  • Classic Consensus: Paxos, Byzantine Fault Tolerance (BFT)
  • Blockchain Consensus: Tendermint, Ouroboros, Bitcoin (PoW), Ethereum (PoS), Polkadot (NPoS)
  • Consensus Properties: Safety, liveness, finality, fault tolerance
  • Comparison: Trade-offs between different consensus mechanisms

Advanced Topics

  • Layer 2: Optimistic rollups, ZK rollups, state channels
  • Cross-Chain: Bridges, validators, multi-chain protocols
  • MEV: Front-running, sandwich attacks, Flashbots
  • Zero-Knowledge: zk-SNARKs, zk-STARKs, privacy
  • Governance: DAOs, proposals, voting, timelocks
  • Oracles: Chainlink, price feeds, custom oracles
  • Account Abstraction: EIP-4337, smart wallets, paymasters

Security & Auditing

  • Common vulnerabilities and exploits
  • Security best practices
  • Audit methodologies
  • Formal verification
  • Bug bounties

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