Smart Contract Requirements and Architecture BBLC Practice Questions (Page 5)

Questions 21–25

1. 21expert · hard

   A cross-border payment dApp needs to settle transactions in fiat currency. The architecture must include a smart contract that holds escrowed funds, an oracle for exchange rates, and a separate contract for user balances. The team is concerned about the cost of frequent oracle updates. Which architecture decision best balances cost and reliability?

   • AHave the smart contract request the exchange rate from the oracle on every transaction.
   • BUse a pull-based oracle where the contract reads a rate that is updated periodically by an off-chain service.
   • CUse a push-based oracle that updates the rate on every block.
   • DHardcode the exchange rate in the contract and update it manually when needed.
   Reveal Solution Discussion Select an answer first
2. 22foundation · easy

   A business analyst is documenting requirements for a smart contract that will handle escrow payments. Which statement is an example of a non-functional requirement?

   • AThe contract must complete a release transaction within 30 seconds of confirmation.
   • BThe contract must record the timestamp of each release.
   • CThe contract must allow either party to initiate a dispute.
   • DThe contract must release funds to the seller only after the buyer confirms receipt.
   Reveal Solution Discussion Select an answer first
4. 23foundation · easy

   Which Solidity pattern is commonly used to restrict a function so that only the contract deployer can execute it?

   • AUsing a require statement that checks the block number
   • BMaking the function internal
   • CDeclaring the function as view
   • DUsing a modifier that compares msg.sender to an owner variable
   Reveal Solution Discussion Select an answer first
5. 24application · medium

   A crop-insurance dApp pays out automatically when rainfall drops below a threshold. The contract needs external weather data. Which integration approach is most appropriate?

   • AUse a decentralized oracle network to bring weather data on-chain.
   • BAsk users to manually submit weather data.
   • CStore weather data off-chain and have the contract read it from a database.
   • DHave the contract fetch data from a public API directly using an HTTP request.
   Reveal Solution Discussion Select an answer first
6. 25expert · hard

   A token contract needs to store a list of addresses that are blacklisted. The list is expected to grow over time, and the team wants to minimize gas for checking if an address is blacklisted during transfers. Which data structure is most gas-efficient?

   • AA linked list of blacklisted addresses.
   • BA dynamic array of blacklisted addresses.
   • CA string containing all blacklisted addresses concatenated.
   • DA mapping from address to boolean indicating blacklist status.
   Reveal Solution Discussion Select an answer first