Blockchain Technology Smart Contract Fundamentals 5

Question 1

What is a 'time lock' contract, and why do DeFi protocols use them?

Accepted Answer

A contract that enforces a mandatory delay between proposing and executing governance changes

Answer

Time locks impose a waiting period (e.g., 48 hours) on admin actions, giving users time to react and exit before potentially harmful changes take effect.

Question 2

What is the purpose of the 'modifier' keyword in Solidity?

Accepted Answer

It defines reusable pre/post condition checks that wrap function execution

Answer

Modifiers inject guard logic (like onlyOwner or nonReentrant) around a function, making access control and validation reusable across many functions.

Question 3

In the context of Ethereum smart contracts, what is 'MEV' (Maximal Extractable Value)?

Accepted Answer

Profit extracted by reordering, inserting, or censoring transactions within a block

Answer

MEV refers to value that block producers (miners/validators) or searchers can capture by controlling transaction ordering, enabling strategies like arbitrage and liquidations.

Question 4

What does the 'immutable' keyword do in Solidity?

Accepted Answer

Allows a variable to be set once at construction and then permanently read-only

Answer

'immutable' variables are written once in the constructor and then inlined into the bytecode, making reads cheaper than storage reads while still being configurable per deployment.

Question 5

What is a 'Soulbound Token' (SBT) as proposed by Vitalik Buterin?

Accepted Answer

A non-transferable NFT permanently linked to a specific wallet as a form of digital identity or credential

Answer

SBTs are non-transferable tokens that represent credentials, achievements, or memberships tied to an individual's on-chain identity, similar to a digital resume.

Blockchain Practice Test

Blockchain Practice Test

Blockchain Technology Smart Contract Fundamentals 5