FREE Blockchain Developer Decentralized Application (dApp) Architecture Questions and Answers Flashcards
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Read the first 6 FREE Blockchain Developer Decentralized Application (dApp) Architecture Questions and Answers flashcards as text
Which layer in a typical dApp architecture is responsible for storing transaction history immutably?
Answer: Blockchain data layer
The blockchain data layer stores all transaction records in an immutable, append-only ledger that cannot be altered after confirmation.
What is the primary purpose of an oracle service in dApp architecture?
Answer: To provide off-chain data to smart contracts
Oracles bridge the gap between blockchains and external systems by feeding real-world data into smart contracts that cannot natively access off-chain information.
In a dApp using the proxy pattern for upgradability, what does the proxy contract primarily store?
Answer: The state variables and a pointer to the logic contract
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.
Why do many production dApps use a subgraph via The Graph protocol instead of reading directly from the blockchain?
Answer: Indexed subgraphs allow fast, complex queries that are impractical with raw RPC calls
The Graph indexes blockchain events into a queryable GraphQL API, enabling complex filtering and pagination that raw RPC endpoints handle poorly.
Which architectural pattern allows a dApp frontend to function even when the user's RPC provider experiences downtime?
Answer: Multi-provider failover with fallback RPC endpoints
Configuring multiple RPC providers with automatic failover ensures the dApp can switch to an available node if the primary provider goes offline.
What is the main security risk of storing sensitive application configuration directly inside a smart contract's state variables?
Answer: All on-chain data is publicly readable regardless of Solidity visibility modifiers
Blockchain state is publicly accessible to anyone inspecting the chain, so marking a variable as private only restricts contract-level access, not external visibility.