Smart Contracts and dApps Flashcards

What is the purpose of the 'require' statement in Solidity?

Answer: To validate conditions and revert the transaction with a message if the condition is false

The require statement checks a condition at runtime; if it fails, it reverts the transaction and optionally provides an error message, refunding remaining gas.

Which design pattern is used in DApps to separate concerns by having a frontend interact with multiple specialized smart contracts rather than one monolithic contract?

Answer: Diamond (EIP-2535) or modular contract pattern

Modular contract patterns like the Diamond standard (EIP-2535) split logic into facets or separate contracts, improving maintainability and enabling upgrades without size limits.

What is 'slippage' in the context of decentralized exchange transactions?

Answer: The difference between the expected token price at order submission and the actual execution price

Slippage occurs because AMM prices shift continuously; a large trade or high volatility can cause the execution price to differ significantly from the quoted price.

In a DAO (Decentralized Autonomous Organization), what mechanism is most commonly used to prevent token holders from voting with borrowed tokens?

Answer: Snapshot-based voting where token balances are recorded at a specific block before the proposal

Snapshot voting records token balances at a specific block height before a proposal is created, preventing vote manipulation through flash loans or late token acquisition.

What is the EVM (Ethereum Virtual Machine) stack-based architecture's maximum stack depth?

Answer: 1024 elements

The EVM has a maximum stack depth of 1024 items; exceeding this limit causes a stack overflow and reverts the transaction.

What problem does the 'commit-reveal' scheme solve in smart contract-based applications?

Answer: It prevents front-running by hiding a user's intent until after the commitment phase

In a commit-reveal scheme, users first submit a hash of their action (commit), then later reveal the actual action, preventing others from copying or front-running the intent.

Which Ethereum Improvement Proposal introduced the concept of 'meta-transactions' to allow users to interact with DApps without holding ETH for gas?

Answer: EIP-4337 (Account Abstraction)

EIP-4337 (Account Abstraction) enables smart contract wallets and paymasters so users can pay gas in tokens or have a relayer sponsor fees, eliminating the need to hold ETH.