Fix Payment Gateway Processing Failures

We are looking for an experienced Payments Integration Engineer to stabilize, enhance, and extend our live production system, specifically across:

Admin dashboard functionality
Multi-provider routing (MID orchestration)
Callback/webhook reliability
Merchant onboarding and provider configuration tools

This is a hands-on, production-critical role requiring strong debugging, payments experience, and the ability to work within an existing deployed ecosystem.

Key Responsibilities
1. Admin Dashboard & Login Fixes
Diagnose and fix issues in the admin login and dashboard pages
Ensure:
Authentication works reliably
Session handling is stable
Dashboard loads without errors
Debug frontend-backend interactions for admin panel
2. MID / Terminal Orchestration (Core Task)
Ensure 10 MID terminals (merchant provider accounts) are:
Properly configured
Actively routing transactions
Respecting priority/fallback logic
Validate:
Routing engine selection
Provider failover behavior
Daily limits and capacity handling
3. Multi-Layer Callback Orchestration
Implement and stabilize callback/webhook orchestration
Ensure:
Provider → SentinelGate → Merchant callback chain works end-to-end
Both SUCCESS and FAILURE events are handled
Transactions move from PENDING → SUCCESS/FAILED correctly
Fix:
Missing callbacks
Incorrect signature validation
Incorrect status mapping
Ensure merchant receives final transaction status reliably
4. Merchant Setup & Provider Integration
Configure and onboard 10 merchant accounts, including:
Provider selection
API credential setup
Currency configuration
MID mapping
Ensure:
Providers are active and functional
Routing is correctly assigned per merchant
Fallback providers exist where required
5. Callback URL Validation & Approval
Configure and validate approved callback URLs
Ensure:
HTTPS endpoints are used
Callback signature verification works
Merchant systems correctly receive POST callbacks
Debug:
missing callbacks
invalid signatures
incorrect endpoints
6. Backend Patch — Provider & Merchant Configuration Tools

Implement a production-ready patch to allow internal staff/admin users to:

Select providers per merchant
Enter and manage provider credentials securely
Configure callback URLs per merchant
Assign MIDs and routing priority
Enable/disable providers dynamically

This must:

Integrate seamlessly into existing Node.js backend
Be compatible with current database schema (Prisma or equivalent)
Include validation and error handling
Avoid breaking live processing
7. Production Debugging & Stability
Investigate live transaction failures
Trace full payment flow:
API → PaymentIntent → Provider → Callback → DB → Merchant
Fix:
stuck transactions
missing records
provider failures
Ensure system is stable under real payment traffic
Technical Environment
Backend: Node.js (TypeScript)
Architecture:
API Gateway (/services/api-gateway)
Core services (svc-rails, svc-routing)
Database: PostgreSQL (Prisma ORM likely)
Deployment: VPS (Linux)
Payment Providers:
Paystack
Seerbit
Emergent
Hubtel
Others (multi-rail orchestration)
Required Skills
Core Technical Skills
Strong Node.js / TypeScript backend development
Experience with REST APIs and service orchestration
Experience working with Prisma or SQL databases
Debugging production systems (logs, DB, APIs)
Payments / Fintech Experience (MANDATORY)
Experience integrating payment gateways (e.g. Paystack, Stripe, Flutterwave, etc.)
Understanding of:
payment flows (auth, capture, settlement)
webhooks/callbacks
transaction states (pending, success, failed)
Experience with:
multi-provider routing
failover systems
merchant account/MID management
Backend Systems & Architecture
Experience with:
microservices or service-based architecture
API gateways
environment-based configs
Ability to trace and debug:
async workflows
callback chains
race conditions
Security & Best Practices
Understanding of:
API key management
webhook signature validation
secure credential storage
Ability to avoid:
exposing sensitive payment data
unsafe DB queries
Frontend (Basic — helpful but not required)
Ability to debug admin/dashboard UI issues (React/Next.js likely)
Fix API integration issues from frontend to backend
Preferred Experience
PSP / payment orchestration platform experience
Experience with:
multi-currency systems
global payment rails
gaming / high-risk merchant flows
Experience deploying to VPS (Linux, PM2/systemd)
Experience with payment link / hosted checkout systems
Success Criteria

The role is successful when:

Admin dashboard is stable and fully functional
All 10 MID terminals are working and routing correctly
Callbacks:
are received
validated
update transactions
notify merchants
10 merchants are fully onboarded and processing
Staff can:
configure providers
manage credentials
assign routing
manage callbacks
No transactions remain stuck in PENDING without resolution
Work Style
Independent, proactive problem solver
Comfortable working on live production systems
Able to read and understand existing codebase quickly
Communicates clearly about:
issues
fixes
risks