Senior SaaS Engineer — Next.js, Supabase & Reusable Architecture | Paid Trial

We are building TN, an existing SaaS product for Australian occupational therapists. The stack is Next.js, React, TypeScript and Supabase/PostgreSQL. The founder can develop features. We need an experienced, hands-on engineer to review the existing foundations and establish clear, reusable patterns so future features and modules can be added consistently. You should have personally shipped and maintained real SaaS products with users, permissions, data and ongoing change. INITIAL ENGAGEMENT: SMALL PAID TRIAL Shortlisted applicants will be invited to a separately agreed US$100 fixed-price trial through Upwork. The posted budget covers this trial only. We will agree and fund the milestone before work starts. Applying does not require unpaid custom work, and submitting a proposal does not guarantee a trial or ongoing contract. The trial will be a bounded review of one representative feature and the shared code needed to understand it. We will agree on a scope intended to fit approximately 2–3 hours; flag any mismatch before accepting. It is not a review of the entire application. Deliver a concise written review covering: 1. What should be retained and why. 2. The three highest-priority improvements, tied to specific code or behaviour, with the risk or benefit of each. 3. A proposed reusable pattern for the feature, including component/service boundaries, data access and permissions where relevant. 4. How a second feature or module would reuse that pattern, and the tests that would demonstrate it works. 5. A small, separately priced implementation milestone, with assumptions and exclusions. No implementation, complete redesign, exhaustive security audit or production changes are included in the trial. Trial material will use synthetic examples and a bounded code sample or development environment. Production credentials and real patient data are not required. Payment is for the agreed trial deliverable, regardless of whether we continue together. POSSIBLE FOLLOW-ON WORK After the review, we may commission a separately scoped milestone to improve one existing feature into a tested reference implementation, document the pattern, and progressively apply it elsewhere. Relevant areas include reusable React components, service boundaries, authenticated data access, Supabase permissions/RLS, error handling and maintainable tests. Retain working foundations where they are sound and explain proposed changes before implementing them. This role centres on architecture and full-stack implementation; brand strategy and a complete visual redesign are separate work. REQUIRED EXPERIENCE AND WORKING APPROACH - Personal, hands-on delivery and maintenance of production SaaS, with examples of what you actually implemented and owned. - Strong recent React and TypeScript experience, plus practical Next.js and PostgreSQL experience. State clearly how much production Supabase experience you have; equivalent PostgreSQL experience must not be presented as Supabase delivery. - Ability to reason about authentication, permissions and data isolation, and to test who may access or change data. - Experience improving an existing codebase incrementally, documenting conventions and making future development easier. - Clear written English for technical explanations and handover. State your available weekly capacity and regular meeting overlap within 9am–5pm Melbourne time. Propose at least a two-hour overlap window on two weekdays; a full Australian working day is not required. - The person we assess must be the person doing the work. Disclose any team members, subcontractors or agency involvement and their responsibilities before agreement. THIS ROLE IS NOT SUITABLE IF - Your examples are limited to landing pages, brochure sites, tutorial projects, UI screenshots or unlaunched demos, with no maintained SaaS delivery to discuss. - Your experience is exclusively Figma/visual design, no-code tools, WordPress or page builders, without hands-on React/TypeScript application work. - You only implement frontend appearance and cannot take responsibility for server-side data access, permission behaviour and relevant tests. - You need this engagement to learn the core stack or cannot independently explain the code and decisions you propose. - You are submitting as a salesperson or intermediary while leaving the actual delivery engineer unnamed, or intend to substitute or outsource the work without agreement. - Your default proposal is a wholesale rewrite, framework migration or replacement of working components before examining the existing product and explaining the need. - You can only provide generic architecture advice or AI-generated recommendations without connecting them to the supplied code. AI-assisted tools are welcome; personal understanding, validation and ownership are required. - You cannot support the agreed Melbourne overlap or provide reliable written progress updates. - You require a large discovery engagement before considering the bounded paid trial, or cannot work within an explicitly agreed scope and price. Please do not submit unrelated portfolio dumps, unverifiable outcome claims or a generic proposal that does not answer the questions below. Redacted examples and a screen-share walkthrough are acceptable where an NDA prevents public links. Do not disclose another client's confidential code or data. YOUR PROPOSAL 1. Give up to two relevant SaaS examples. Explain your personal contribution, one shared pattern you established, and what happened after launch. Include a live link, permitted code sample or a description of evidence you can show privately. 2. Describe one inherited-codebase improvement: what you retained, what you changed, and how you checked for regressions or permission problems. 3. Summarise your recent Next.js, React/TypeScript, PostgreSQL and production Supabase experience separately. Be direct about gaps. 4. Confirm whether the US$100 review format works for you, or explain the smaller scope you would need within that budget. No custom review is required in your application. 5. State your proposed ongoing hourly rate, whether a steady 10–15 hours per week would change that rate, your available capacity, Melbourne overlap, and who would personally deliver the work. Ongoing hours are a possibility, not a guarantee. We will compare evidence, practical judgement, clarity, maintainability and total cost. The lowest bid alone will not determine selection. Any further work will be agreed separately through Upwork.