Senior Full-Stack Developer for Hotel Payment Processor Migration | React, Node.js, PostgreSQL, AWS

We are looking for an experienced Senior Full-Stack Developer to help with an ongoing hotel software project and lead the migration of our live production payment system to a new payment processor. This is an existing production system used by an active hotel, not a new application. The current payment processor is integrated across approximately 5 interconnected programs/services, so the migration needs to be carefully planned, tested, and executed without disrupting hotel operations or customer payments. Responsibilities Review and understand the existing full-stack architecture Map the current payment flow across all connected systems Integrate the new payment processor Update frontend and backend payment functionality Implement and validate payment APIs and webhooks Handle payment authorization/capture, refunds, cancellations, and failure scenarios Maintain transaction consistency across connected systems Review PostgreSQL data models and payment records Test the new integration in staging/sandbox environments Create a safe production migration and rollback strategy Perform the live production cutover Monitor and troubleshoot the system after migration Improve existing code where necessary Maintain AWS, Docker, CI/CD, and deployment infrastructure Required Technical Skills React Next.js JavaScript / TypeScript Node.js PostgreSQL REST APIs Payment gateway / payment processor integrations Webhooks AWS Docker CI/CD DevOps Git/GitHub What We're Looking For We especially want someone who has experience migrating payment processors in an existing production application. Experience integrating Stripe, Adyen, Checkout.com, Braintree, PayPal, or similar payment platforms is highly relevant, but we're more interested in your ability to safely understand and migrate a complex existing payment flow than experience with one specific provider. Because this is a live hotel, reliability is critical. We need someone who thinks carefully about data integrity, duplicate transactions, idempotency, webhook delivery, pending transactions, refunds, reconciliation, rollback procedures, monitoring, and production failure scenarios. The initial priority is the payment processor migration, but this is an ongoing full-stack project, so there is potential for continued development work after the migration. When Applying Please briefly describe: A payment processor or payment gateway integration/migration you've completed. Whether you've migrated payments in an already-live production system. How you would approach switching processors when the payment flow touches multiple applications/services. Your experience with React/Next.js, Node.js, PostgreSQL, AWS, Docker, and CI/CD. Your availability to support the system during the production cutover. We are looking for someone who can understand the existing system first, develop a safe migration plan, and then execute the switch with minimal risk to live hotel operations.