Start by clarifying requirements and defining the core data models (Account, Customer, Transfer) with their relationships and state transitions. Then, walk through each operation, specifying the API contract, error cases, and complexity, while highlighting design trade-offs and optimizations.
Pro tip: Emphasize idempotency and atomicity for financial operations, and discuss how you would handle concurrency and consistency in a real system, even if the implementation is single-threaded.
Ask clarifying questions about expected scale, concurrency, persistence, and exact semantics of operations like transfers and merges. Confirm assumptions before diving into design.
Specify the fields and relationships for Account, Customer, and Transfer, including state (e.g., pending, accepted, expired) and invariants like non-negative balances. Explain how merging customers affects account ownership.
For each operation, define input parameters, return values (e.g., success/failure, transaction IDs), and error conditions (e.g., insufficient funds, duplicate transfer, expired hold). Discuss idempotency keys for safety.
State the time and space complexity for each operation, assuming appropriate data structures (e.g., hash maps for O(1) lookups). Mention potential optimizations like indexing or caching for high throughput.
Highlight design trade-offs (e.g., consistency vs. availability) and how you would extend the system for concurrency, persistence, or distributed deployment.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.