Blockchain Architecture and Platforms
This domain examines how ledgers are structured and how major platforms differ. Expect questions that map a requirement set - privacy between counterparties, known identities, no cryptocurrency, deterministic finality - onto an architecture or product, and questions on node roles, consensus families and smart-contract execution.
Core rules
- Typical layers: network (P2P gossip), consensus (ordering and agreement), data (blocks, state, indexes) and application (contracts, APIs).
- Permissionless networks (public Ethereum, Bitcoin) admit anyone; permissioned networks (Hyperledger Fabric, Corda, Quorum) require membership and identity.
- Hyperledger Fabric: peers execute chaincode, an ordering service orders transactions, channels partition ledger visibility, and MSP identities replace anonymous accounts. There is no gas and no native coin.
- Ethereum: account model (EOA and contract accounts), EVM bytecode, gas metered per opcode, and probabilistic finality under PoW or checkpointed finality under PoS.
- Corda: point-to-point exchange of states, notary services for uniqueness, and restricted data dispersal rather than global broadcast.
- Bitcoin uses the UTXO model; Ethereum uses balances. Consensus families differ: PoW probabilistic, PoS economic, PBFT-style deterministic.
Worked example
Eight banks want a trade-finance ledger. Transactions must be visible only to the two counterparties, participants are known legal entities, and settlement must be final without a volatile coin. Fabric fits: each bank runs a peer, channels or private data collections isolate deal data, the Raft ordering service orders transactions, and chaincode enforces terms. Reasoning: identity is handled by MSP, privacy is enforced at the channel level, and finality comes from the ordering and endorsement policy rather than mining economics. A public Ethereum deployment would expose state and require gas.
Traps
- Describing Fabric as “Ethereum with permissions”; it has a different execution and ordering model.
- Assuming Corda broadcasts every state to all parties.
- Treating PoW confirmation counts as absolute finality.
- Believing a private network is automatically secure; membership and endorsement policies still need design.
- Forgetting that smart contracts cannot natively read external data without an oracle.