CCE Blockchain Fundamentals & Architecture 3 — Questions and Answers
Question 1: What distinguishes a permissioned blockchain from a permissionless blockchain?
- Permissioned blockchains use Proof-of-Work exclusively
- Permissioned blockchains restrict participation to approved entities, while permissionless allow anyone (Correct answer)
- Permissioned blockchains are always public and visible to all
- Permissioned blockchains cannot execute smart contracts
Correct answer: Permissioned blockchains restrict participation to approved entities, while permissionless allow anyone
Permissioned blockchains (e.g., Hyperledger Fabric) require identity verification and approval before participation, enabling enterprise use cases with privacy and compliance requirements.
Question 2: What is the role of a 'full node' in a blockchain network?
- It only stores block headers to save disk space
- It downloads, validates, and stores the entire blockchain and enforces consensus rules (Correct answer)
- It only processes and broadcasts transactions without validation
- It serves as a centralized authority that confirms blocks for light clients
Correct answer: It downloads, validates, and stores the entire blockchain and enforces consensus rules
Full nodes independently download every block and transaction, verify all consensus rules, and maintain a complete copy of the blockchain, making them the backbone of network security.
Question 3: In blockchain terminology, what is 'block finality'?
- The maximum size a block can reach before being split
- The point at which a block is considered irreversible and cannot be reorganized out of the chain (Correct answer)
- The process of archiving old blocks to save storage
- The event when all pending transactions in a mempool are confirmed
Correct answer: The point at which a block is considered irreversible and cannot be reorganized out of the chain
Finality refers to the guarantee that a confirmed block will not be reversed; PoW chains have probabilistic finality while PoS chains like Ethereum can achieve economic finality through slashing.
Question 4: What is the 'mempool' (memory pool) in a blockchain node?
- A cache of recently validated blocks awaiting archival
- A holding area for valid but unconfirmed transactions waiting to be included in a block (Correct answer)
- The RAM allocated to running smart contract execution
- A pool of mining nodes coordinating to find blocks
Correct answer: A holding area for valid but unconfirmed transactions waiting to be included in a block
The mempool is an in-memory buffer on each node storing valid transactions that have been broadcast but not yet included in a confirmed block.
Question 5: What is a 'soft fork' in the context of blockchain protocol upgrades?
- A fork that creates two permanent competing chains with equal validity
- A backward-compatible upgrade where old nodes still accept new blocks but may not understand new rules (Correct answer)
- A forced upgrade requiring all nodes to update within a set deadline or be expelled
- A rollback of the chain to an earlier state after a bug is discovered
Correct answer: A backward-compatible upgrade where old nodes still accept new blocks but may not understand new rules
A soft fork tightens consensus rules so new blocks remain valid under old rules, making the upgrade backward-compatible — old nodes don't update but continue accepting the chain.
Question 6: What does 'sharding' aim to solve in blockchain architecture?
- The inability to use smart contracts on UTXO-based blockchains
- Scalability by partitioning the network so each node only processes a subset of transactions (Correct answer)
- The privacy problem of transparent public ledgers
- Double-spending attacks by splitting attacker resources
Correct answer: Scalability by partitioning the network so each node only processes a subset of transactions
Sharding splits the blockchain into parallel partitions (shards), each processing its own subset of transactions, so total throughput scales with the number of shards.
Question 7: Which consensus mechanism do most enterprise blockchains (e.g., Hyperledger Fabric) use instead of Proof-of-Work?
- Proof-of-Authority or Byzantine Fault Tolerant (BFT) variants (Correct answer)
- Proof-of-Work with lower difficulty targets
- Delegated Proof-of-Stake with public token voting
- Proof-of-Burn with token destruction
Correct answer: Proof-of-Authority or Byzantine Fault Tolerant (BFT) variants
Enterprise chains prefer PoA or BFT-style consensus (e.g., PBFT, Raft) because known validators can reach fast, energy-efficient finality without competitive mining.
CCE Blockchain Fundamentals & Architecture 3
What distinguishes a permissioned blockchain from a permissionless blockchain?