A27 · Design a Banking App A27 · 设计银行应用
Verified source经核实出处
Prompt: "Design a Banking App." — interviewing.io. Credibility C/D.
Core concerns (traditional SD)核心考察（传统系统设计）
- Double-entry ledger: every transfer = two entries (debit + credit). Enforce
SUM(balance) = 0invariant.双重记账：每次转账 = 两条记录（借 + 贷）。强制SUM(balance) = 0不变量。 - Idempotent transfers: idempotency_key; safe retries.幂等转账：idempotency_key；重试安全。
- Two-phase commit or saga for cross-account / cross-system transfers.两阶段提交或Saga用于跨账户/跨系统转账。
- Audit log: append-only, cryptographically chained entries.审计日志：追加式、密码学链接条目。
- Fraud detection: rules + ML model; decision latency < 100ms.反欺诈：规则 + ML；决策延迟 < 100ms。
Data model数据模型
Account(account_id, owner_id, currency, status)
LedgerEntry(entry_id, account_id, amount, currency, ref_tx_id, created_at)
-- Invariant: for each tx, SUM(entries.amount) = 0
Transaction(tx_id, idempotency_key, status, initiated_at)