Senior Full-Stack Engineer (TypeScript, React, Node, PostgreSQL) for Healthcare Billing SaaS

Senior Full-Stack Engineer (TypeScript, React, Node, PostgreSQL) for Healthcare Billing SaaS Summary We are looking for a senior full-stack engineer to help maintain and grow a production healthcare SaaS platform used by emergency medical service (EMS) agencies and their billing teams. This is not a greenfield project. The application is live, has daily users, and handles real money and protected health information. It covers ambulance claim billing, payment posting, HR and payroll, crew scheduling, dispatch, training, and a mobile app for field staff. We are onboarding new client agencies over the next few months, and support volume is growing with them. We need a second engineer who can take a reported problem or a scoped feature and carry it all the way to production: database, API, web screen, and mobile screen. Our stack: • TypeScript everywhere. • React web app (React Query, Zod). • React Native mobile app (Expo). • Node.js and Express API, background workers, Socket.IO. • PostgreSQL with SQL migrations. • AWS (ECS, RDS, S3, CloudWatch, Bedrock, Textract), managed with CDK. • GitHub Actions CI, automated tests, and AI code review on every pull request. THE ROLE You will work alongside our existing senior engineer, an engineering lead, and a product manager. Work arrives as Linear tickets that have already been clarified and prioritized. Most tickets cross the whole stack: a bug a biller reports usually involves a query, an API rule, and a screen. You will own tickets end to end. That means finding the real cause, fixing it at the right layer, testing it, and getting it through review and into production safely. WHAT YOU WILL DO • Fix production bugs reported by billers, HR staff, supervisors, and field crews. • Build features across the database, API, web app, and mobile app. • Write PostgreSQL migrations and queries that are safe on live data. • Work on billing logic: claims, payer rules, payment posting, corrections, and patient statements. • Work on operational modules: scheduling, time off, payroll export, help desk, and training. • Build and fix financial and operational reports that finance teams rely on. • Investigate production alarms, errors, and slow queries using logs and metrics. • Write meaningful tests, including the failure and edge cases. • Review AI-generated code, including your own, before it reaches production. • Respond to code review feedback and keep pull requests small and clear. • Write clear notes on tickets so the product manager and billers can verify the fix. HOW WE WORK Our team uses AI development tools heavily for investigation, drafting, and first implementations. We need someone who makes that faster and safer, not someone who ships whatever the tool produces. We need someone who can: • Understand how a biller or supervisor actually works before changing anything. • Trace a problem from the screen down to the data, and fix the cause rather than the symptom. • Recognize when a change could move money, expose patient data, or break an existing workflow. • Critically review AI-generated code and push back when it is wrong. • Ask the product manager good questions when a requirement is unclear. • Coordinate with the other engineer so work does not overlap or conflict. • Communicate clearly in writing with non-technical teammates. REQUIRED EXPERIENCE • Strong production experience with TypeScript, React, and Node.js. • Strong SQL and PostgreSQL experience, including migrations on live databases. • Experience building complex business applications, not only marketing sites. • Experience designing and changing REST APIs. • Debugging production issues using logs, metrics, and database queries. • Automated testing on both frontend and backend. • Git and pull-request-based development with code review. • Experience handling sensitive data carefully (access control, audit trails, least privilege). • Strong written and spoken English. • At least 1 to 2 hours of reliable overlap with US Eastern Time for handoff. • Comfortable working asynchronously from written tickets, with clear written handoff notes at the end of each day. STRONG ADVANTAGES • Healthcare billing or revenue cycle software, especially EDI (837 claims, 835 remittances, 270/271 eligibility, 276/277 claim status). • HIPAA or SOC 2 environments. • React Native or Expo production experience. • Payroll, scheduling, or other workflow-heavy operational software. • AWS (ECS, RDS, CloudWatch) and infrastructure-as-code. • Financial reporting where totals must reconcile to the penny. • Experience working successfully with AI-assisted development. • A main working day that falls overnight in US time. ENGAGEMENT DETAILS • Long-term, full-time hourly engagement (about 40 hours per week). • Open to candidates in any time zone. Overnight US coverage is a plus, but skill and judgment come first. • A short daily overlap with US Eastern Time (early morning or late evening ET) for handoff and questions. • Paid, clearly scoped trial: one real ticket taken from investigation to merged pull request. • Individual freelancers only. • You must personally perform all work. • No subcontractors, no shared accounts, and no one else accessing our code or systems. • You will sign a confidentiality agreement and a HIPAA business associate agreement before receiving access. TO APPLY Please answer the following questions in your proposal: 1. Describe a production application you worked on across both frontend and backend. Which parts did you personally build? 2. Tell us about a hard production bug you tracked down. How did you find the real cause, and how did you make sure it stayed fixed? 3. Describe a database change you made on a live system with real data. How did you make it safe? 4. Have you worked on healthcare billing, insurance, payroll, or other software where mistakes cost real money? What did you learn? 5. How do you use AI development tools, and how do you check that AI-generated code is correct before it ships? 6. What tests do you consider essential before releasing a change that touches money or patient data? 7. Describe your React Native experience. If it is not a strength, say so directly. 8. What time zone are you in, what are your normal working hours, and which 1 to 2 hours can you reliably overlap with US Eastern Time? 9. Will you personally perform all work and be the only person accessing our code and systems? Please include links to relevant work, code samples, or a GitHub profile, and explain exactly what you contributed to each. Generic proposals that do not answer these questions will not be considered.