API Development
Documented, versioned APIs that let banks and fintechs expose products to partners safely — designed to be easy to integrate and hard to misuse.
- Spec-first
- OAuth 2.0
- Versioned
APIs partners can integrate in days, not months.
We design and build the APIs that sit between your core systems and the partners, apps, and services that depend on them — with clear contracts, strong authentication, and documentation that's actually kept up to date. Every API ships with versioning and sandbox access from day one.
Built to be easy to integrate, and hard to misuse.
What We Deliver
Six areas of work that make up most API development engagements.
API Design & Specification
Resource models, schemas, and a versioning strategy defined before a line of code is written.
REST & Event-Driven APIs
Synchronous and event-driven endpoints, built to a consistent contract.
Authentication & Access Control
OAuth 2.0, API keys, and scoped access so partners see only what they should.
API Gateway & Rate Limiting
Traffic management, throttling, and quotas that protect core systems under load.
Versioning & Documentation
Interactive, kept-current documentation for every supported API version.
Partner Onboarding & Sandbox
Sandbox environments and onboarding flows that get partners integrated quickly.
Our Process
A five-stage engagement, from contract design to live monitoring.
Define
Design the API contract: resources, schemas, and versioning strategy.
Secure
Build in authentication, authorization, and rate limiting from the start.
Build
Implement and test endpoints against the published specification.
Document
Publish interactive documentation and sandbox access for partners.
Monitor
Track usage, latency, and errors after every release.
Fintech Application Development
Customer and back-office applications for regulated products.
Payment Systems Engineering
Payment switches, gateways, and settlement flows.
Microservices Architecture
Domain-driven services that scale independently.
Legacy Modernisation
Phased modernisation of core and legacy platforms.
Let's design your next API.
Tell us what you're building or modernising — a member of the Unlock team will get back to you.