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

The blockchain data layer stores all transaction records in an immutable, append-only ledger that cannot be altered after confirmation.

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

Oracles bridge the gap between blockchains and external systems by feeding real-world data into smart contracts that cannot natively access off-chain information.

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

A proxy contract holds the application state and delegates calls to a separate logic contract, allowing the logic to be replaced without losing stored data.

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

The Graph indexes blockchain events into a queryable GraphQL API, enabling complex filtering and pagination that raw RPC endpoints handle poorly.

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

Configuring multiple RPC providers with automatic failover ensures the dApp can switch to an available node if the primary provider goes offline.

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