InterviewCompany
Payments, data correctness, APIs, reliability, and product-quality engineering practice.
Use idempotency keys and store request-result mappings safely.
If a client retries after a timeout, the same key should return the same result instead of double-charging. Handle key expiry and request mismatch carefully.
Compare ledgers, detect mismatches, classify differences, and create audit trails.
Financial systems need immutable records, clear source of truth, retry-safe jobs, and explainable correction flows.
Clear docs, predictable errors, versioning, SDKs, and stable contracts.
Developer experience depends on fast integration, good examples, helpful error messages, test environments, and backward compatibility.
Track attempts, authorization rate, failure reasons, latency, and provider health.
Break metrics by payment method, region, bank, merchant, and release. Alert on meaningful drops and separate customer errors from system errors.