A CIO's Guide to API-First Integration in Banking
API-first is easy to say and hard to do at a bank, where decades of systems were never designed to talk to anything. This guide covers the architecture and governance that turn "we have APIs" into a genuinely connected ecosystem.
Contracts before code
API-first means the interface is designed and agreed before implementation, so producers and consumers can build in parallel against a stable contract. Versioning and backward compatibility are governance decisions, not afterthoughts — breaking a contract breaks everyone downstream.
Events for the things that change
Request/response APIs are right for queries and commands; events are right for state changes. A bank that publishes domain events — payment cleared, limit changed, customer updated — lets new capabilities subscribe without touching the systems of record.
Govern the ecosystem
A developer portal, sandbox, standard security patterns and clear ownership turn a pile of endpoints into a platform teams and partners actually adopt. Governance is what keeps an API estate from decaying into the next generation of legacy.
- Agree API contracts before implementation, and version them
- Publish domain events so new capabilities plug in cleanly
- Treat the portal, sandbox and governance as the real platform
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