Blockchain Architecture & Design Principles Flashcards

What is the primary advantage of using a directed acyclic graph (DAG) topology instead of a linear chain for blockchain data structure?

Answer: Higher throughput by allowing parallel block confirmation without a single chain bottleneck

DAG-based ledgers (e.g., IOTA's Tangle, Hedera Hashgraph) allow multiple blocks or transactions to be confirmed in parallel, dramatically increasing theoretical throughput.

In a blockchain solution design, what does 'chain reorganization' (reorg) imply for application developers?

Answer: Previously confirmed transactions may be replaced if a longer competing chain emerges

A reorg replaces a portion of the canonical chain with a longer fork, potentially reversing transactions that appeared confirmed, requiring developers to wait for sufficient confirmations.

Which approach best supports regulatory compliance requirements like data deletion (GDPR right to erasure) in a blockchain system?

Answer: Use cryptographic commitments on-chain with personal data stored off-chain in a deletable store

Keeping personal data off-chain (deletable) while committing only a hash or pointer on-chain satisfies GDPR erasure rights without violating blockchain immutability.

What is the architectural purpose of a 'channel' in Hyperledger Fabric?

Answer: To create isolated sub-networks with their own ledger, enabling data privacy between participant subsets

Channels in Fabric create private communication sub-networks; only channel members see transactions, allowing different consortia to share infrastructure while keeping data confidential.

When designing tokenomics for a blockchain protocol, what does 'token velocity' indicate about economic health?

Answer: How frequently tokens change hands; high velocity can reduce the incentive to hold and depress price

High token velocity means tokens are quickly spent rather than held, weakening demand and potentially destabilizing the token's value in the ecosystem.

Which architectural characteristic makes blockchain-based systems inherently resistant to retroactive data tampering?

Answer: Chained cryptographic hashes where each block references its predecessor's hash

Each block header contains the hash of the previous block; altering any historical block changes its hash, invalidating all subsequent block hashes and requiring re-mining the entire chain.

In the context of Layer 2 scaling, what is the key difference between an optimistic rollup and a ZK-rollup?

Answer: Optimistic rollups assume validity and rely on fraud proofs during a challenge window, while ZK-rollups post cryptographic validity proofs immediately

Optimistic rollups (e.g., Arbitrum, Optimism) have a dispute window (days) for fraud challenges, while ZK-rollups (e.g., zkSync, StarkNet) finalize as soon as the validity proof is verified on L1.