CCE Blockchain Fundamentals 4 — Questions and Answers
Question 1: What does 'immutability' mean in the context of blockchain?
- Transaction data can be updated by the original sender at any time
- Once data is recorded on-chain, it cannot be altered without redoing all subsequent work (Correct answer)
- Nodes can prune old transaction records to save disk space
- Smart contracts can be patched by the contract owner post-deployment
Correct answer: Once data is recorded on-chain, it cannot be altered without redoing all subsequent work
Blockchain immutability means historical records are cryptographically locked; changing one entry would require recalculating all subsequent blocks.
Question 2: What is a 'light client' (SPV node) in a blockchain network?
- A node that mines blocks at reduced power consumption
- A node that downloads only block headers to verify payments without full validation (Correct answer)
- A smart contract deployed on a sidechain
- A hardware wallet with limited key storage capacity
Correct answer: A node that downloads only block headers to verify payments without full validation
SPV (Simplified Payment Verification) clients download only block headers and use Merkle proofs to verify transactions without storing the full chain.
Question 3: What distinguishes a public blockchain from a consortium blockchain?
- Public blockchains use PoW; consortium blockchains always use PoS
- Public blockchains are open to anyone; consortium blockchains are governed by a group of organizations (Correct answer)
- Public blockchains have lower transaction fees
- Consortium blockchains support smart contracts; public ones do not
Correct answer: Public blockchains are open to anyone; consortium blockchains are governed by a group of organizations
A consortium blockchain is controlled by a pre-selected group of organizations, while a public blockchain allows open participation from anyone.
Question 4: In blockchain systems, what is meant by 'throughput'?
- The maximum size of a single transaction in bytes
- The number of nodes a transaction must pass through before confirmation
- The number of transactions a network can process per unit of time (Correct answer)
- The time between a transaction broadcast and its first confirmation
Correct answer: The number of transactions a network can process per unit of time
Throughput, often measured in transactions per second (TPS), quantifies how much transaction volume a blockchain network can handle.
Question 5: What is a 'sidechain' in blockchain architecture?
- A duplicate copy of the main chain maintained for disaster recovery
- A separate blockchain that runs in parallel and is pegged to a main chain (Correct answer)
- A secondary hash produced by each block header
- A read-only snapshot of a blockchain at a specific block height
Correct answer: A separate blockchain that runs in parallel and is pegged to a main chain
A sidechain is an independent blockchain linked to a parent chain via a two-way peg, enabling asset transfers and experimental features without risking the main chain.
Question 6: What is the double-spending problem that blockchain technology solves?
- The risk that two transactions share the same fee amount
- The ability of a digital asset owner to spend the same coins more than once (Correct answer)
- The computational overhead of verifying duplicate blocks
- The scenario where two miners find valid blocks simultaneously
Correct answer: The ability of a digital asset owner to spend the same coins more than once
Digital files can be copied freely, so without blockchain consensus, a user could broadcast the same digital coin to multiple recipients; the chain enforces a single valid spending order.
Question 7: What happens during a blockchain 'reorganization' (reorg)?
- Nodes compact the UTXO set to reduce disk usage
- The network switches to a longer competing chain, orphaning recently confirmed blocks (Correct answer)
- Miners redistribute hash power to balance block times
- Smart contracts are redeployed to updated bytecode
Correct answer: The network switches to a longer competing chain, orphaning recently confirmed blocks
A reorg occurs when a longer fork overtakes the current chain tip, causing nodes to roll back recent blocks and adopt the new heavier chain.
CCE Blockchain Fundamentals 4
What does 'immutability' mean in the context of blockchain?