In banking IT, APIs used to be an internal detail.
Now they sit at the center of digital channels, partner ecosystems, and open banking regulations.

Designing an API strategy deliberately is becoming as important as choosing a core banking platform.

Think in domains, not just endpoints

Instead of designing APIs screen by screen, start with domains:

• Accounts and balances
• Payments and transfers
• Cards, loans, and savings products
• Customer identity and consents

Define clear ownership and boundaries for each domain, then design APIs around stable business concepts, not UI flows.

Separate internal, partner, and public APIs

Not every consumer of your APIs needs the same surface area.

• Internal APIs power your own web and mobile channels.
• Partner APIs support vetted third parties with contracts and SLAs.
• Public/Open Banking APIs meet regulatory specs and are tightly scoped.

Use different gateways, authentication methods, and rate limits to reflect these differences, even when they share underlying services.

Security and compliance by design

Banking APIs must satisfy:

• Strong authentication (OAuth2/OIDC, mutual TLS where needed).
• Fine-grained authorization and consent management.
• Full audit logs for requests, responses, and changes.

Design consent flows and data minimization early so you don’t end up leaking more customer data than required.

Observability for APIs, not just apps

Treat APIs as first-class products with:

• Latency, error rate, and availability SLAs.
• Dashboards per domain and per consumer.
• Alerting on unusual patterns (suspicious access, spikes from a single client).

With the right architecture, banking IT teams can move from “pipes behind channels” to a platform that supports new products, partners, and regulations with far less friction.