Blockchain and Web3 Interview Questions for Indian Companies 2026

These core concepts appear in every blockchain engineering interview in India regardless of role seniority.

Blockchain architecture: a distributed ledger where each block contains a hash of the previous block, a timestamp, and transaction data. Immutability comes from the chain: changing a block invalidates all subsequent blocks. Consensus mechanisms: Proof of Work (Bitcoin): computationally expensive, energy-intensive; Proof of Stake (Ethereum post-Merge): validators stake ETH, selected probabilistically. PoS uses ~99.95% less energy than PoW. Public vs private blockchain: public (anyone can join, read, write: Ethereum, Bitcoin); private (permissioned: Hyperledger Fabric, used in enterprise supply chain, banking). Cryptographic foundations: hash functions (SHA-256: one-way, deterministic, avalanche effect), digital signatures (ECDSA: private key to sign, public key to verify), and Merkle trees (efficient transaction verification without downloading full blocks).

Solidity and smart contract development is the most tested technical skill for Web3 developer roles in India.

Solidity basics: statically typed, compiled to EVM bytecode. State variables, functions, events, modifiers, mappings, arrays. Data locations: storage (persistent, expensive), memory (temporary, cheaper), calldata (read-only, cheapest for external function arguments). Common question: 'What is the difference between storage and memory in Solidity?' Security patterns: reentrancy attacks (the DAO hack): fixed with checks-effects-interactions pattern or ReentrancyGuard. Integer overflow/underflow (fixed in Solidity 0.8+ with automatic revert). Access control (OpenZeppelin Ownable, AccessControl). Gas optimisation: packing variables into 32-byte slots, using uint256 over smaller types (paradoxically cheaper), avoiding loops over unbounded arrays in production contracts. ERC standards: ERC-20 (fungible tokens), ERC-721 (NFTs), ERC-1155 (multi-token standard).

Indian crypto companies hiring for protocol engineering roles test DeFi concepts specifically.

AMM (Automated Market Maker): Uniswap's x*y=k constant product formula: how liquidity pools work, impermanent loss explained. Common question: 'Explain impermanent loss to a non-technical stakeholder.' Lending protocols: Aave, Compound: overcollateralisation, liquidation threshold, interest rate models. Flash loans: uncollateralised loans that must be repaid in the same transaction: used for arbitrage and collateral swaps. Layer 2 scaling: Rollups (Optimistic vs ZK): Optimistic rollups assume validity, have fraud proof window; ZK rollups use cryptographic validity proofs, faster finality. Polygon (Indian company) is the leader in ZK rollup infrastructure.

Knowing the Indian Web3 landscape helps you contextualise the interview at specific companies.

CoinDCX: India's largest crypto exchange by volume. Tech stack: Go, React, Kubernetes. Interview: backend systems for high-throughput order books, wallet security. CoinSwitch: consumer-focused crypto app. Interview: product thinking + backend for transaction management. Polygon (AggLayer): Bengaluru-based ZK rollup infrastructure company. Interview: cryptography, EVM internals, ZK proof systems (advanced). Zebi/Sentinel Protocol/other fintech: enterprise blockchain on Hyperledger Fabric for supply chain, trade finance. Interview: Hyperledger Fabric channels, chaincodes (Golang), permissioned blockchain vs public chain trade-offs. Remittance/cross-border: Stellar, Ripple (XRP Ledger): used by Indian fintech for international payments. Know the technical architecture.

The blockchain job market in India is volatile but the underlying demand for Web3 engineers is real.

Salary ranges: Junior blockchain developer (0–2 years): ₹10–20 LPA. Mid-level Solidity developer: ₹20–40 LPA. Senior Web3 engineer at a protocol company: ₹50–1 Cr (often paid partially in tokens). Market reality: 2022–2023 crypto winter reduced hiring significantly. 2025–2026 saw renewed growth: Polygon, Coinbase India, and Indian Web3 startups are actively hiring again. Token compensation: many Web3 companies in India offer 10–20% of total compensation in tokens. Treat this as high-risk: value it conservatively. Skills that transfer: Solidity, cryptography, distributed systems, and ZK proof knowledge are highly transferable to traditional fintech, banking (CBDCs), and enterprise security roles.