- Banking APIs have stricter error-handling expectations than typical consumer SaaS APIs.
- Reconciliation logic needs to catch discrepancies between your records and the bank's.
- Every request and response involving money movement needs a compliance-grade audit log.
- Sandbox testing against realistic edge cases matters more here than in most integrations.
Banking APIs demand stricter error handling
A typical SaaS integration can tolerate a failed request with a simple retry. A banking API failure involving an actual money movement needs far more careful handling — idempotency to prevent duplicate transactions, explicit handling of partial failures — because the stakes of getting it wrong involve real customer funds.
Reconciliation catches what error handling misses
Even with careful error handling, a fintech product needs an ongoing reconciliation process that compares its own transaction records against the bank's, catching any discrepancy quickly rather than discovering it weeks later during an audit or a customer complaint.
Test against realistic edge cases in sandbox
Banking partner sandboxes support testing scenarios like partial failures, timeouts, and unusual account states that a typical integration test suite might skip. Deliberately testing against these realistic edge cases before going live catches problems that only show up under real-world conditions.