Full Stack Engineer

Sell It or No is a mobile-first online auction marketplace that gives sellers unique control over bid acceptance. The platform features real-time bidding, AI-assisted listing creation, Stripe payment processing with auth holds, comprehensive shipping coordination, vehicle and real estate transaction workflows, a full admin center, and advertising integrations. The product is in active development targeting a quick launch and needs a skilled engineer to carry it across the finish line.

Engagement Type

• Contract to start with a strong path to hire for the right candidate
• Post-launch support retainer expected
• Mostly Remote, but must be able to meet in person in or near Milwaukee, WI or Chicago, IL as part of interview and on occasion during role.

What You’ll Be Doing

• Launch preparation - finish remaining features, resolve open issues, and harden the product for go-live
• Testing - write and execute integration/end-to-end tests; manually verify critical user flows (bidding, checkout, payments, shipping)
• Security review - audit API endpoints, rate limiting, session handling, input sanitization, Stripe webhook verification, and auth flows; fix any findings
• Performance optimization - database query analysis, Redis cache tuning, frontend bundle sizing, pagination, and image delivery
• Code quality - address tech debt, enforce TypeScript strictness, clean up dead code
• Post-launch support - monitor production logs, triage bugs, ship hotfixes, support feature requests

Do you have experience in TypeScript?, * 3+ years of professional full-stack development (TypeScript required - both frontend and backend)

• Solid React - hooks, query management, complex component state
• Node.js / Express - REST API design, middleware, async patterns
• PostgreSQL - query writing, schema design, indexing, migrations
• Stripe API - PaymentIntents, SetupIntents, webhooks, Connect
• Experience with WebSockets or other real-time patterns
• Comfortable reading and improving an existing large codebase (~400 API routes, 200+ frontend files)
• Familiarity with security best practices: auth, input validation, rate limiting, OWASP top 10
• Ability to write tests and document findings

Nice to Have

• Experience with Drizzle ORM or similar TypeScript ORMs
• Redis (pub/sub, caching, distributed locks)
• EasyPost or other shipping API experience
• OpenAI / LLM API integration experience
• React Native / Expo - the mobile prototype will eventually need parity with the web
• Prior work on marketplace or auction platforms
• Familiarity with shadcn/ui or Radix UI component patterns

What a Strong Candidate Looks Like

• Can orient themselves quickly in a large codebase without hand-holding
• Writes clean TypeScript - no any escapes, proper Zod schema validation
• Understands the full request lifecycle (browser * API * DB * response * UI update)
• Proactive communicator - flags blockers early, documents decisions

$120,000 - $160,000 a year - Temporary, Full-time