Blockchain Quiz

The internal specifier limits access to derived contracts only, reducing attack surface and inheritance misuse.

Delegatecall shares storage between contracts; mismatched layouts can overwrite variables and cause exploits.

Retention captures wallet-level engagement and recurring activity — a Tier-2 metric for real community stickiness.

Echidna auto-generates random inputs to stress invariants, uncovering deep logic vulnerabilities.

Mainnets often have stricter gas limits and higher costs than testnets. A function that runs fine on testnet may exceed block gas limits in production. Developers should simulate deployments and optimize loops before mainnet release

The fallback() function runs when a transaction calls a non-existent function or sends data without matching any signature. It’s essential for proxy contracts but must be written carefully to avoid gas griefing and reentrancy risks.

delegatecall lets one contract run another’s code while keeping its own storage and balance. It’s powerful but risky — if the target contract has malicious logic, it can overwrite your state variables or drain funds. Auditors always flag unsafe delegatecalls

Rollups are Layer 2 blockchain scaling solutions that bundle multiple transactions off-chain and then post cryptographic proofs to the main chain. This reduces gas fees and increases transaction speed while maintaining the security and decentralization of the base blockchain. Rollups are key to Ethereum scalability and the future of high-performance Web3 applications.

MEV (Maximum Extractable Value) refers to profits gained by reordering or inserting transactions in a block. It’s a major focus in blockchain security and DeFi optimization, influencing how validators and searchers interact with the mempool.

Sharding is a blockchain scalability technique that divides the entire network’s data into smaller, manageable pieces called shards. Each shard processes its own transactions and smart contracts, improving network speed, performance, and efficiency. This concept is key for scalable blockchain infrastructure like Ethereum 2.0 and future Web3 ecosystems.

A Blockchain QA Analyst is responsible for testing smart contracts, dApps, and blockchain networks to ensure they work as intended. They identify bugs, check performance, and validate security, which is critical for building trust in decentralized applications. This role is increasingly important in blockchain careers, as companies rely on QA analysts to deliver reliable and secure Web3 products.

Bitcoin uses the SHA-256 cryptographic hash function to secure transactions and link blocks in the blockchain. This algorithm produces a fixed 256-bit output, ensuring immutability and resistance to tampering. By using SHA-256, Bitcoin maintains trust, decentralization, and data integrity across the network

zk-SNARKs are zero-knowledge proofs that improve blockchain privacy and scaling by verifying transactions without revealing sensitive data.

BFT-based (Byzantine Fault Tolerant) consensus mechanisms achieve instant or near-instant finality by requiring agreement among validators in just one round of communication, allowing transactions to be finalized in seconds—faster than PoW, PoS, or DPoS.

BFT-based (Byzantine Fault Tolerant) consensus mechanisms achieve instant or near-instant finality by requiring agreement among validators in just one round of communication, allowing transactions to be finalized in seconds—faster than PoW, PoS, or DPoS.

The Ethereum Virtual Machine (EVM) is a global, decentralized computer that executes smart contracts on the Ethereum blockchain. It ensures every node produces the same results, keeping the network consistent and secure.

Traders exploit transaction ordering for profit.

A 51% attack happens when one miner/validator controls over half the network’s power or stake. This lets them rewrite history or double-spend coins, threatening security. It’s rare on large chains like Bitcoin but a risk for smaller ones.

OpenZeppelin offers audited, reusable smart contract templates, like ERC-20 and ERC-721 implementations. It enhances security and saves development time.

Ganache creates a local Ethereum blockchain for development and testing. It allows developers to deploy contracts and simulate transactions without real ETH.