No prep material for this one since it wasn't circulating anywhere.
Start by clarifying requirements: transaction volume, query patterns, consistency needs, and regulatory constraints. Then design a data model that captures transactions as immutable ledger entries, and propose a scalable storage and indexing strategy to support efficient queries. Discuss trade-offs between consistency, availability, and latency, and how to handle double-spending and idempotency.
Pro tip: Emphasize idempotency and exactly-once processing for transaction ingestion, as crypto systems must handle retries and network partitions without duplicating entries. Also, mention the importance of auditability and compliance (e.g., KYC/AML) in the design.
Ask about expected transaction volume, read/write ratio, query patterns (e.g., by user, by block, by time), consistency requirements, and regulatory needs. Define functional and non-functional requirements.
Propose a schema for transactions, blocks, addresses, and balances. Use an append-only ledger with unique transaction IDs and references to previous transactions to ensure immutability and traceability.
Select a database (e.g., relational for ACID, NoSQL for scale) and design indexes to support common queries. Consider partitioning by time or user, and caching for hot data.
Discuss sharding, replication, and consensus mechanisms (e.g., Raft, Paxos) for distributed consistency. Address how to handle double-spending and ensure idempotent writes.
Compare SQL vs NoSQL, strong vs eventual consistency, and latency vs throughput. Discuss handling of forks, reorgs, and failed transactions, and how to ensure auditability.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.