Blockchain Developer Decentralized Application (dApp) Architecture 2

Question 1

In a typical dApp stack, what role does the smart contract layer primarily serve?

Accepted Answer

Backend business logic and state on-chain

Answer

Smart contracts act as the on-chain backend, holding state and enforcing business logic deterministically.

Question 2

Which library is most commonly used by a dApp frontend to interact with an EVM blockchain?

Accepted Answer

ethers.js

Answer

ethers.js (and web3.js) provide JavaScript APIs to read contracts and send transactions.

Question 3

Why are decentralized storage systems like IPFS used in dApps instead of storing files on-chain?

Accepted Answer

On-chain storage is expensive and limited

Answer

Storing large files on-chain costs enormous gas, so dApps store data off-chain and keep only the hash on-chain.

Question 4

What does a wallet like MetaMask provide to a dApp architecture?

Accepted Answer

Key management and transaction signing

Answer

Wallets manage the user's private keys and sign transactions without exposing the keys to the dApp.

Question 5

Which component lets a dApp efficiently query historical and aggregated on-chain data?

Accepted Answer

An indexer like The Graph

Answer

Indexing protocols like The Graph parse events into queryable subgraphs since blockchains are poor at complex queries.

Blockchain Practice Test