# Software Technical Specification: B2B Fraud Detection Gateway ## SECTION 1: SYSTEM ARCHITECTURE & TECH STACK TAXONOMY - Architectural Pattern: Event-driven microservices built on Apache Kafka for high-throughput transaction streaming. - Tech Stack Selection: React (Frontend), Go / Golang (High-concurrency backend services), PostgreSQL (Transactional data), Redis (Cache layer). ## SECTION 2: DATABASE SCHEMA & DATA MODELING - Entity-Relationship Framework: * `Users` table -> linked to `Merchants` (1:N) via `merchant_id` foreign key. * `Transactions` table indexed on `created_at` and `risk_score` for rapid fraud query execution. - Data Flow Architecture: Payment API request -> Kafka stream -> ML scoring microservice -> Ledger entry. ## SECTION 3: API SPECIFICATION & INTEGRATION ENDPOINTS - RESTful Protocols: * `POST /v1/transactions/charge`: Accepts payload containing amount, currency, and payment token; returns risk status. - Third-Party Integrations: Stripe Connect API for settlement and Twilio API for 2FA step-up authentication. ## SECTION 4: DEVOPS, SECURITY & SCALABILITY INFRASTRUCTURE - Security Architecture: TLS 1.3 encryption, mTLS for internal microservice communication, and PCI-DSS Level 1 compliance isolation. - CI/CD Infrastructure: Kubernetes clusters deployed on AWS EKS with horizontal pod auto-scaling triggered at 70% CPU usage.