Senior Full-Stack Developer to Finish & Launch a SaaS Web App

Senior Full-Stack Developer to Finish & Launch a SaaS Web App We have a self-serve SaaS web app that's mostly built and working. We're looking for an experienced developer to take it the final stretch — finish the remaining pieces, QA it thoroughly, make it secure, and help us launch quickly. This is a senior role. We need someone who has built and launched real SaaS products before and can work independently — not someone learning on the job. What you'll do - Finish the remaining features and make sure the whole app works reliably end to end (not just the happy path) - Run a proper QA pass — edge cases, error handling, user flows, data integrity, behavior under load - Harden the app for security — auth, input validation, protection against common attacks, safe handling of user data and secrets - Get it deployment-ready and help us launch You must know and have hands-on experience with - JavaScript / Node.js (ES modules) — backend, serverless functions, and a vanilla-JS/HTML frontend (no React or front-end framework) - PostgreSQL, specifically via Supabase (schema, migrations, auth, row-level security) - Vercel deployment (serverless functions + static frontend) - Anthropic / Claude API — prompting, streaming responses, managing usage and cost - Apify — running and integrating scraping/data actors - Transactional email with Postmark and/or Resend (deliverability, templates, webhooks) - Web application security — you can independently find and fix vulnerabilities (auth, secrets handling, rate limiting) - QA — you test your own work rigorously and think like both an attacker and a user Nice to have - Stripe or similar payments/billing integration (likely to be added) - Prior experience shipping AI/LLM product features To apply, please include: 1. Links to 2+ SaaS products you've shipped, and your role on each 2. A security or QA issue you caught and fixed — what it was and how 3. In your own words: how you'd approach finishing and safely launching a nearly-done Applications that skip these will not be considered.