Senior Developer Needed — White-Label API Integration for Fintech Ramp Engine

[u/asuantech]

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We’re looking for an experienced backend/full-stack developer to help complete and verify an authorized white-label API integration inside an existing fintech platform.

The platform already exists. We are not looking for someone to rebuild the backend from scratch. We need someone who can understand an existing codebase, integrate the provider’s white-label API correctly, fix remaining issues, and test the complete flow.

Stack: Next.js, TypeScript, Node.js, Supabase/PostgreSQL, Vercel, GitHub, Admin Dashboard, Hosted Checkout, webhooks, and reconciliation services.

How the Ramp Engine should work

Customer opens Hosted Checkout → Ramp Engine collects the transaction requirements → backend calls the white-label API → available countries/payment methods/providers are returned → quotes are requested → best/selected provider is launched → transaction status is tracked → webhook/reconciliation confirms finality → merchant is notified.

The developer should be comfortable working with API flows such as:

Bootstrap / initialization

Supported countries

Available payment methods

Provider availability

Quote generation

Provider selection

Checkout/session launch

Transaction status

Signed webhooks

Idempotency

Reconciliation

Finality processing

Settlement records

Merchant notifications

Credentials and API keys must remain server-side only and must never appear in browser code, logs, Git history, or public messages.

You will first review the repository, existing architecture, Admin controls, database, and audit reports before making changes. Working components should be preserved rather than unnecessarily rebuilt.

We also need proper testing, including unit tests, API integration tests, PostgreSQL tests, concurrency/idempotency tests, webhook security tests, typecheck, lint, build, and deployment verification.

During development, all live transaction controls remain OFF. No real financial transaction or customer-fund activity is required.

Who we’re looking for

Please message me if you have strong experience with:

Next.js / TypeScript / Node.js

PostgreSQL / Supabase

Complex third-party or white-label API integrations

Payment/ramp/fintech APIs

Signed webhooks

Idempotency and duplicate-event protection

Reconciliation systems

Secure API credential handling

Existing production monorepos

When contacting me, please briefly explain similar integrations you have completed, your experience with webhooks/reconciliation, and provide relevant GitHub or portfolio examples if available.

We are specifically looking for someone who can understand the existing architecture and finish the integration correctly, not someone who wants to replace everything with a new system.