Blockchain Developer Decentralized Application Architecture 2

Question 1

In a typical dApp architecture, what is the primary role of the smart contract layer?

Accepted Answer

Encoding and enforcing the application's business logic and state transitions

Answer

Smart contracts hold the trustless business logic and on-chain state for a dApp.

Question 2

Why do most dApps store large files on IPFS or Arweave rather than directly on-chain?

Accepted Answer

On-chain storage is extremely expensive per byte and bloats the chain

Answer

Storing bytes on-chain costs significant gas, so dApps store content off-chain and keep only the hash on-chain.

Question 3

What does a 'content-addressed' storage system like IPFS use as a file identifier?

Accepted Answer

A cryptographic hash of the content (CID)

Answer

IPFS addresses content by a hash of its bytes, so the same content always yields the same CID.

Question 4

Which component lets a browser-based dApp frontend submit transactions signed by the user?

Accepted Answer

A wallet provider injecting an Ethereum provider object

Answer

Wallets like MetaMask inject a provider that the frontend uses to request signatures and send transactions.

Question 5

What is the main purpose of an indexing layer such as The Graph in a dApp stack?

Accepted Answer

To efficiently query and serve historical/aggregated on-chain data

Answer

Indexers transform raw chain events into queryable APIs since reading aggregated data directly from a node is slow.

Blockchain Practice Test