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Project / completed
Enterprise multi-tenant payment gateway integrated with Cybersource for secure transaction orchestration.
Role
Senior Full Stack Engineer
Status
completed
Overview
Designed and developed an enterprise-grade payment gateway platform focused on secure multi-tenant transaction processing. The platform centralized authentication, authorization, tenant isolation, and transaction orchestration, enabling multiple business units to operate under a unified architecture while maintaining strong security boundaries and operational independence.
Architecture
Monolithic architecture built with ASP.NET Core MVC using Razor Views for server-rendered UI, Material UI for component styling, IdentityServer for authentication and authorization, PostgreSQL for persistence, and Cybersource as the external payment provider.
Tech Stack
Backend
Frontend
Authentication
Security
Database
Integration
Key Contributions
Designed the multi-tenant authentication and authorization model.
Implemented secure payment processing flows with Cybersource integration.
Built tenant-aware transaction orchestration and validation pipelines.
Developed role-based access control and permission management.
Implemented audit logging for financial traceability.
Created transaction monitoring dashboards for internal operations.
Engineering Decisions
The platform was designed as a multi-tenant system within a single ASP.NET Core application. Tenant context was incorporated into authentication, authorization, transaction processing, and data access so multiple business units could share the platform while maintaining clear operational boundaries.
Authentication and authorization were centralized through IdentityServer, using OAuth2 and JWT for secure identity propagation. Role-based access control and tenant-aware permissions were handled as platform concerns instead of being implemented independently by each module.
Integration with Cybersource was kept behind a controlled transaction flow responsible for request preparation, signing, validation, provider communication, and transaction lifecycle handling. This reduced duplicated integration logic and kept payment behavior easier to maintain.
The architecture prioritized predictable transactional behavior over introducing unnecessary distributed components. Keeping the core payment workflow within one application boundary simplified consistency, validation, and operational support while responsibilities remained separated internally.
Audit logging was incorporated into the payment workflow so relevant transaction and authorization activity could be traced during operational investigation and support.
Internal dashboards exposed transaction activity and processing state to the teams responsible for operating the platform. The goal was not only to execute payment flows, but also to make their behavior easier to inspect and support.
Key Challenges
Designed tenant isolation within a monolithic architecture while preserving scalability.
Solved Cybersource request signing, validation, and transaction lifecycle management.
Implemented centralized authentication flows across multiple tenants using IdentityServer.
Ensured transactional consistency and security across payment operations.
Security Considerations
Authorization decisions considered both the authenticated user and the active tenant context. Roles and permissions were evaluated within that scope to reduce the risk of users operating outside their authorized business unit.
The platform used IdentityServer as the centralized identity authority, with OAuth2 and JWT supporting authenticated application flows. Centralizing authentication helped avoid duplicated security logic across tenants and modules.
Requests sent to Cybersource followed a controlled request construction, signing, validation, and response-handling process. Provider-specific security logic remained inside the payment integration boundary rather than being distributed across the application.
Sensitive transaction orchestration, authorization checks, and validation remained on the server side. Client-facing interfaces were treated as input channels rather than trusted sources for transaction validity.
Relevant transaction and authorization activity was recorded to provide a clearer operational history and support investigation when payment issues required analysis.
Application workflows and persistence operations incorporated tenant context so one business unit could not unintentionally operate on another tenant’s transaction scope.
Impact
Successfully deployed into production in an enterprise environment.
Improved payment reliability across multiple business units.
Reduced onboarding complexity for new tenants.
Strengthened security, auditability, and operational monitoring.
Established a scalable authentication foundation for future platform growth.