CBSA Blockchain Architecture & Design Principles 4 — Questions and Answers
Question 1: Which data structure allows efficient membership proofs in a blockchain without revealing all stored elements?
- Binary search tree
- Merkle Patricia trie (Correct answer)
- Bloom filter
- Skip list
Correct answer: Merkle Patricia trie
The Merkle Patricia trie (used in Ethereum) supports efficient O(log n) inclusion proofs and state lookups while encoding all state in a single root hash.
Question 2: In a federated Byzantine agreement (FBA) model like Stellar, how is consensus reached?
- All nodes must agree simultaneously in a single round
- Each node chooses its own quorum slice, and consensus emerges from overlapping slices (Correct answer)
- A committee of elected miners approves each block
- A single leader proposes and all validators accept or reject
Correct answer: Each node chooses its own quorum slice, and consensus emerges from overlapping slices
FBA allows each node to define which other nodes it trusts (quorum slices); global consensus emerges when slices overlap sufficiently.
Question 3: What is the purpose of a 'genesis block' in blockchain design?
- It contains the algorithm for selecting future validators
- It is the hardcoded first block that establishes the initial chain state (Correct answer)
- It stores the private keys of founding network participants
- It defines the maximum supply of the native token
Correct answer: It is the hardcoded first block that establishes the initial chain state
The genesis block is block zero, hardcoded into the client software; it anchors the entire chain history and sets initial parameters like difficulty or token allocations.
Question 4: Which architectural consideration is most critical when integrating an oracle into a blockchain solution?
- Ensuring the oracle uses the same consensus algorithm as the chain
- Preventing single-oracle dependency to avoid a central point of failure and manipulation (Correct answer)
- Storing oracle source code on-chain for transparency
- Requiring oracles to operate as full nodes
Correct answer: Preventing single-oracle dependency to avoid a central point of failure and manipulation
A single oracle is a centralized trust point; decentralized oracle networks (e.g., Chainlink) aggregate data from multiple sources to prevent manipulation and downtime.
Question 5: In Hyperledger Fabric's architecture, what component is responsible for ordering transactions into blocks?
- Endorsing peer
- Anchor peer
- Ordering service (orderer) (Correct answer)
- Certificate Authority
Correct answer: Ordering service (orderer)
The ordering service in Fabric receives endorsed transactions, sequences them deterministically, and cuts them into blocks distributed to committing peers.
Question 6: What is the role of 'gas' in Ethereum's architecture beyond paying for computation?
- It determines block producer election weight
- It prevents infinite loops and denial-of-service attacks by metering resource consumption (Correct answer)
- It represents the miner's share of the block reward
- It controls the maximum number of validators per epoch
Correct answer: It prevents infinite loops and denial-of-service attacks by metering resource consumption
Gas limits bound the resources any single transaction can consume, making it economically infeasible to execute infinite loops or overwhelm nodes with computation.
Question 7: Which consensus approach prioritizes consistency over availability when a network partition occurs?
- Proof of Work
- Nakamoto consensus
- PBFT and most classical BFT protocols (Correct answer)
- Avalanche protocol
Correct answer: PBFT and most classical BFT protocols
Classical BFT protocols halt rather than produce inconsistent state during a partition, placing them in the CP quadrant of the CAP theorem.
CBSA Blockchain Architecture & Design Principles 4
Which data structure allows efficient membership proofs in a blockchain without revealing all stored elements?