Smart Contracts and dApps Flashcards
7 cards from real Blockchain Technology practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Smart Contracts and dApps flashcards as text
What is 'flash loan' arbitrage in DeFi?
Answer: Borrowing and repaying assets within a single transaction to profit from price differences
Flash loans allow uncollateralized borrowing within one atomic transaction; if not repaid with fees in the same block, the entire transaction reverts.
Which tool is most commonly used to test Solidity smart contracts locally?
Answer: Hardhat or Foundry local development frameworks
Hardhat and Foundry provide local Ethereum node emulation, test runners, and debugging tools for smart contract development and testing.
What is 'front-running' in the context of Ethereum smart contracts?
Answer: Inserting a transaction ahead of a known pending transaction to profit from it
Front-running occurs when a miner or bot spots a profitable pending transaction in the mempool and submits their own transaction with higher gas to execute first.
In Solidity, what does the 'modifier' keyword allow developers to do?
Answer: Reuse pre- and post-condition checks across multiple functions
Modifiers wrap functions with reusable logic (e.g., access checks), using the '_' placeholder to indicate where the modified function's body executes.
What is the 'Merkle tree' used for in the context of smart contracts and NFT whitelists?
Answer: Efficiently verifying membership in a large set without storing the full list on-chain
A Merkle tree allows a contract to verify whether an address is in a whitelist by checking a small proof against a root hash stored on-chain, saving gas.
What is 'slippage tolerance' in a DEX swap transaction?
Answer: The maximum acceptable price change between submitting and executing a swap
Slippage tolerance sets a floor on the minimum tokens received; if market movement causes the output to fall below it, the transaction reverts.
Which Ethereum scaling solution uses fraud proofs and requires a challenge period for withdrawals?
Answer: Optimistic Rollup
Optimistic Rollups assume transactions are valid by default and rely on fraud proofs during a 7-day challenge window before finality on L1.