Backend Developer for Web & Mobile

Job Title: Senior Backend Developer – Payments and Transaction Platform Company: Digital World Enterprises Inc. Employment Type: Full-time or long-term contract Location: Remote Experience: 5+ years preferred About the Role Digital World Enterprises Inc. is hiring an experienced backend developer to help take over, stabilize, improve, and operate an existing production web and mobile platform. The platform includes user accounts, balances, payments, withdrawals, transaction records, notifications, administrative tools, and third-party integrations. The developer must be comfortable reviewing code created by another team and safely preparing it for production under new management. Responsibilities Review and document the existing backend codebase and system architecture Set up the application in development, staging, and production environments Maintain APIs, databases, background jobs, and administrative systems Manage user accounts, balances, transactions, payments, and withdrawals Integrate and maintain payment processors, ACH providers, KYC services, and other third-party APIs Prevent duplicate payments, withdrawals, and webhook processing Review and improve database structure, migrations, backups, and recovery procedures Identify security, performance, and reliability risks Build automated tests for important financial and account functions Configure logging, monitoring, alerts, and error reporting Work with frontend, mobile, DevOps, compliance, and management teams Document deployment, rollback, disaster-recovery, and support procedures Required Knowledge Strong experience with the backend language and framework used in the transferred platform REST API development and third-party API integrations PostgreSQL, MySQL, or another relational database Authentication, authorization, OAuth, JWT, and session management Payment processing, ACH, webhooks, refunds, and transaction states Financial ledgers, wallet balances, or transaction-based systems Idempotency and prevention of duplicate transaction processing Background jobs, message queues, and scheduled tasks GitHub or GitLab, branches, pull requests, and code reviews Docker and CI/CD pipelines AWS, Google Cloud, Azure, or similar cloud infrastructure Secrets management, encryption, rate limiting, and API security Production debugging, monitoring, backups, and rollback procedures Preferred Experience Taking over and modernizing an existing production platform Payment, fintech, marketplace, sportsbook, prediction-market, sweepstakes, or other transaction-heavy platforms KYC, identity verification, fraud detection, and geolocation integrations High-availability systems and sensitive financial data Mobile application backend support SOC 2, PCI, privacy, or other security and compliance requirements