Fintech systems fail in subtle ways: duplicate payments, delayed settlements, and incomplete audit trails. Architecture must prevent those classes of bugs.
Define clear domain boundaries — accounts, payments, ledger, compliance — with explicit ownership of data and APIs.
Make every money-moving operation idempotent. Use keys, outbox patterns, and careful retry semantics.
Prefer event-driven workflows for asynchronous steps, but keep a strong source of truth for balances and ledgers.
Instrument everything: traces, metrics, structured logs, and business KPIs like authorization rate and settlement lag.
Bake compliance into the platform: immutable audit logs, least-privilege IAM, encryption in transit and at rest, and change control.
Hemant Consultancy Services uses this checklist when modernizing payment platforms that must scale past hundreds of thousands of daily transactions.