Blockchain Developer FREE Blockchain Developer Decentralized Application (dApp) Architecture Questions and Answers 2

Question 1

Which layer in a typical dApp architecture is responsible for storing transaction history immutably?

Accepted Answer

Blockchain data layer

Answer

Presentation layer

Answer

API gateway layer

Answer

Caching layer

Question 2

What is the primary purpose of an oracle service in dApp architecture?

Accepted Answer

To provide off-chain data to smart contracts

Answer

To compile Solidity code into bytecode

Answer

To manage user authentication tokens

Answer

To optimize gas fees for transactions

Question 3

In a dApp using the proxy pattern for upgradability, what does the proxy contract primarily store?

Accepted Answer

The state variables and a pointer to the logic contract

Answer

The application business logic

Answer

Only event logs for the frontend

Answer

Compiled ABI definitions for the UI

Question 4

Why do many production dApps use a subgraph via The Graph protocol instead of reading directly from the blockchain?

Accepted Answer

Indexed subgraphs allow fast, complex queries that are impractical with raw RPC calls

Answer

Direct blockchain reads are forbidden by EVM rules

Answer

Subgraphs automatically fix smart contract bugs

Answer

Subgraphs eliminate the need for smart contracts entirely

Question 5

Which architectural pattern allows a dApp frontend to function even when the user's RPC provider experiences downtime?

Accepted Answer

Multi-provider failover with fallback RPC endpoints

Answer

Singleton contract pattern

Answer

Removing all blockchain dependencies from the UI

Answer

Using only WebSocket connections

Question 6

What is the main security risk of storing sensitive application configuration directly inside a smart contract's state variables?

Accepted Answer

All on-chain data is publicly readable regardless of Solidity visibility modifiers

Answer

State variables consume too much gas to read

Answer

State variables cannot be updated after deployment

Answer

Ethereum nodes refuse to store large strings