Senior Backend Developer

Job Title

Senior Backend Developer — Web Marketplace, Auction & Payment System

About the Project

We are building a web-based marketplace platform that connects customers who need building or construction contractors with verified contractors through an auction/bidding system.

The platform will allow customers to post construction project requests, contractors to submit bids, customers to select contractors, and payments to be processed through an Indonesian payment gateway. The flow will include escrow-style payment tracking, manual admin payout approval, transaction logs, and an internal admin dashboard.

We are looking for a Senior Backend Developer to build the backend system, database, payment integration, and core business logic.

Responsibilities

1. Design and build backend APIs for the customer web-app, contractor portal, and admin dashboard.
2. Design database structure for users, contractors, projects, bids, auctions, payments, payouts, refunds, disputes, and audit logs.
3. Build authentication and role-based access control for customer, contractor, admin, and finance/admin users.
4. Develop the project posting, auction, bidding, contractor selection, and project status logic.
5. Integrate with Indonesian payment gateway providers.
6. Build secure payment webhook/callback handling.
7. Develop escrow-style payment status tracking, including unpaid, pending, paid, active, payout requested, payout approved, disbursed, cancelled, refunded, and disputed.
8. Build manual admin payout approval logic.
9. Prevent duplicate payment or payout processing through proper backend safeguards.
10. Create transaction logs and audit logs for important system actions.
11. Support deployment, server setup, staging/production environment, and monitoring.
12. Work closely with the Project Manager, frontend developer, UI/UX designer, and QA tester.
13. Write clean, maintainable, well-documented, and secure backend code.

Must-Have Requirements

1. Minimum 4+ years of backend development experience.
2. Strong experience building REST APIs or GraphQL APIs.
3. Strong experience with PostgreSQL, MySQL, or similar relational databases.
4. Experience with backend frameworks such as Node.js/NestJS, Laravel, Go, or similar.
5. Experience designing transaction-heavy systems.
6. Experience with authentication, authorization, and role-based permissions.
7. Experience integrating third-party APIs.
8. Experience handling payment gateway webhooks/callbacks.
9. Experience deploying backend applications to production.
10. Strong understanding of database consistency, transaction status, and error handling.
11. Able to work independently and make technical decisions.

Nice-to-Have Requirements

1. Experience integrating Indonesian payment gateways.
2. Experience building marketplace, fintech, escrow, payment, auction, procurement, construction, or e-commerce platforms.
3. Experience with Docker, CI/CD, AWS, GCP, DigitalOcean, Railway, Render, or similar.
4. Experience building or supporting admin dashboards.
5. Understanding of basic security practices for payment-related systems.
6. Experience with audit logs, transaction logs, and reconciliation.
7. Experience with file storage such as AWS S3, Cloudflare R2, Firebase Storage, or similar.

Expected Deliverables

1. Backend API for customer, contractor, and admin modules.
2. Database schema and documentation.
3. Authentication and role-based access system.
4. Project and bidding backend logic.
5. Payment gateway integration.
6. Webhook handling system.
7. Payment and payout status system.
8. Transaction and audit logs.
9. Deployment-ready backend system.
10. API documentation for frontend integration.