Senior Full-Stack Developer | Next.js, Node.js, MongoDB | Implementation, Review & Testing

Remote freelance contract | Fixed-price milestones Experience: 8+ years of professional software development About Us Beryl is an investment advisory and technology firm with deep domain expertise in Capital Markets and Private Markets. We are building Beryl Elites X, a platform connecting institutional allocators, fund managers, and financial service providers through networking, company and fund research, due diligence, events, and subscriptions. We seek a hands-on senior developer to improve our existing Phase 1 application and deliver agreed Phase 2 priorities, working directly with the Product Owner. What You’ll Do - Build frontend and backend features from specifications and Figma designs. - Debug, review, and improve existing code while preventing regressions. - Implement data models, business workflows, REST APIs, and third-party integrations. - Enforce secure access across organizations, roles, subscriptions, and documents. - Combine hands-on implementation with review and integration of AI-assisted work. - Own initial QA through AI-assisted testing, automated tests, and manual verification. - Support UAT, resolve defects, and prepare releases with clear test evidence and documentation. Every delivered feature must be tested and personally verified. You must personally review all delivered code, including AI-generated code and tests. Automated checks or AI review alone are insufficient. Required Experience - 8+ years of professional software development, including hands-on ownership of complex web applications. - Strong React, Next.js, Node.js, and TypeScript skills. - MongoDB data modeling, indexing, and data integrity. - Maintaining, debugging, and extending existing applications. - Server-side authentication, authorization, and resource-level permissions. - REST APIs and third-party integrations. - Automated testing, API testing, and hands-on browser verification. - Effective use of AI development and testing tools, with independent verification. - Git, CI/CD, production troubleshooting, and clear communication. Preferred Experience - MongoDB transactions and permission-aware Atlas Search. - AWS SNS/SQS and reliable asynchronous processing. - CI/CD pipeline ownership and Playwright/Cypress. - Maintaining and testing existing payment integrations. - B2B SaaS, fintech, or complex document-access workflows. Redis, Elasticsearch, Firebase, or Zoom experience is relevant only where inherited code actually uses those technologies; these are not requirements for new architecture. Engagement and Delivery We target an agreed release scope within six months. Milestone 1 is Phase 1 baseline and first remediation: establish a reproducible application baseline and deliver agreed fixes with reviewed code, regression tests and staging verification. The Product Owner also contributes code. Subsequent fixed-price milestones have agreed deliverables, acceptance criteria and dates. The schedule includes implementation, human code review, testing, UAT, defect resolution and release preparation. You own the quality of your implementation and the work you review and integrate. The Product Owner sets priorities, accepts business outcomes, and authorizes releases. To Apply Please include: 1. Your years of experience and recent work with Next.js, Node.js, and MongoDB. 2. A comparable delivery, specifying which parts you personally implemented, reviewed, tested, and released. 3. An example of a difficult bug or access-control issue you resolved. 4. How you review and integrate AI-assisted work and personally verify results. 5. The monthly capacity you can commit and how you budget implementation, review, and testing time. 6. Your hourly rate, timezone, earliest start date, and willingness to quote fixed-price milestones after reviewing the code and requirements. Shortlisted candidates will be invited to a technical discussion about their experience and delivery approach.