Senior Full-Stack Developer / Founding Product Engineer

The role at a glance
I'm hiring a senior full stack developer to turn a working TikTok Shop prototype into a secure, subscription SaaS product that sellers can sign up for and use on their own.

Focus
SaaS product development, ecommerce integrations, automation
Engagement
Independent contractor, contract to hire, or full time
Location
Remote, with working hours and communication cadence agreed together
Long term
Technical partner for additional business tools after this first product
About the opportunity
Our first product is a TikTok Shop management platform for sellers. It pulls shop operations, promotions, catalog management, profit reporting, orders, returns, affiliate outreach, content planning, and automation into one workspace.
This is not a website design job. I need someone who can own the technical path from prototype to a maintainable, commercially usable product, and who can explain decisions clearly to a nontechnical founder. Beyond this product, I want a long term partner who can help build more tools and reuse the right foundations across them.
Where the product stands today
We have a real codebase and a published demo, not a blank page concept.
What exists: Node.js, TypeScript, server rendered HTML, CSS and JavaScript, SQLite, and Docker. The app has account login, sample data dashboards, business logic tests, and code for several external integrations.
What is missing:

• The published version is demo only. Live merchant integrations have not been validated end to end.
• The local database is not suitable for durable, multi customer production use.
• Automated jobs are disabled in the demo.
• Customer onboarding, subscriptions, and multi tenant access still need to be built.

You will d ---------- what is worth keeping, what to refactor, and what to replace. I value a thoughtful migration plan far more than an automatic recommendation to rewrite everything.
What you will own
1. A customer ready SaaS product

• Self service signup: customers create a workspace, connect their own shop, invite teammates, choose a plan, and manage their account without developer help.
• Multi tenant architecture with strict separation of customer data, shop connections, background jobs, files, and permissions.
• Support for multiple shops per workspace where it makes sense, built to grow without a premature enterprise rebuild.
• Subscription billing, plan entitlements, usage limits, cancellation handling, and an internal support and admin interface kept separate from customer shop permissions.

2. Reliable TikTok Shop and third party integrations

• Full TikTok Shop integration: app configuration, OAuth, secure token storage, refresh and expiry handling, shop selection, reconnect flows, and deauthorization.
• Evaluate the developer app and distribution model needed to serve independent sellers, not just my own shop.
• Prepare technical materials for platform review, and clearly flag any business, legal, or compliance submissions I need to handle. Platform approval is never assumed.
• Validate API scopes, regional behavior, pagination, webhooks, rate limits, and API version changes. Treat TikTok Shop access and TikTok content publishing access as separate authorizations.
• Build further integrations in an agreed order, potentially Printify, Shopify, YouTube, Instagram, Pinterest, and email . Where a provider can't support something, say so plainly instead of faking it as a live feature.

3. Safe, trustworthy shop workflows

• Promotions and catalog: flash sale management and renewal, bulk product edits, previews, validation, progress tracking, and partial failure handling.
• Reporting: product level profit, costs, shipping, fees, refunds, settlements, ad spend, and exports, with estimates clearly separated from finalized numbers.
• Orders and returns: operational alerts, fulfillment integrations, return workflows, and configurable rules with customer approvals.
• Growth and content: goals, affiliate workflows, content planning, and authorized publishing or analytics where the APIs allow it.

Any action that changes prices, issues refunds, creates orders, or publishes content needs audit logs, preview or dry run modes, explicit permissions, and sensible limits. Retried jobs and repeated webhooks must never cause duplicate actions.
4. Production infrastructure and reliability

• Move persistent data out of the temporary container filesystem into a managed database and object storage.
• Separate development, staging, and production environments with isolated credentials and test data.
• Real queues and scheduled workers instead of relying on a web server staying awake, with job status, retries, idempotency, concurrency controls, alerts, and useful failure messages.
• Deployment pipelines, database migrations, monitoring, backups, restore procedures, and rollback.
• Automated checks for tenant isolation, permissions, critical business logic, and integration behavior.

5. Building with me and supporting future products

• Turn business ideas into clear technical requirements, prioritize the smallest useful release, and ship in reviewable increments.
• Explain tradeoffs in plain English, demo working features regularly, and raise blockers before they become surprises.
• Build reusable foundations (authentication, billing, integration adapters, background jobs) only where reuse is justified. No speculative frameworks.
• Keep the code readable, with architecture notes, setup instructions, operational docs, and a handoff another developer could follow.
• Keep repositories, cloud accounts, domains, and service access under company ownership.

What you bring
You have built and maintained a real SaaS product used by external customers, not only demos or marketing sites.
Required

• Full stack JavaScript and TypeScript, including Node.js backends and usable, responsive interfaces
• Relational databases: schema design, migrations, and multi tenant data isolation
• OAuth, server side secrets, token lifecycle management, and third party API integrations
• Background jobs, queues, webhooks, rate limiting, retries, and idempotent processing
• Subscription billing and authorization based on customer plans and roles
• Cloud deployment, Docker, automated testing, CI/CD, monitoring, and production debugging
• Comfort inheriting existing code, reviewing AI assisted prototypes critically, and improving them without unnecessary rewrites
• Clear communication, real ownership, and sound product judgment

Strong advantage

• TikTok Shop or other marketplace seller APIs
• Shopify, Printify, or social publishing APIs
• Ecommerce financial reconciliation
• Subscription products and integration heavy automation platforms

I'm open to well reasoned changes in framework, database, or hosting. The goal is dependable delivery, not following a technology trend.
Initial milestones
These are outcome based. We'll agree on scope, sequencing, estimates, and budget after the first assessment.
1. Technical assessment and release plan. Review the codebase and integrations, identify security and reliability gaps, recommend a practical architecture, and define a narrow first paid release. List external approvals and dependencies separately from engineering work.
2. Production foundation. Durable storage, customer workspaces, access controls, separate environments, deployment checks, and operational visibility.
3. Live shop pilot. Connect a properly authorized pilot shop, validate an agreed set of real data workflows, and prove that one customer can't access another customer's records or credentials. External API approvals are a dependency, not a guaranteed date.
4. Paid beta. Self service onboarding, subscriptions, the prioritized workflows, support tooling, and documented recovery procedures. New features come only after the core product is reliable.
What success looks like

• Customers connect their own shops and use the product with no manual database edits or developer intervention.
• Customer data stays isolated.
• Reports clearly separate real, estimated, and unavailable data.
• Background jobs are observable and never duplicate business actions.
• Deployments and recovery are repeatable.
• I understand the roadmap, and another engineer could maintain the product.

How to apply
Please include:
1. Two or three relevant SaaS or integration projects, your specific role, and whether you maintained them after launch.
2. Your experience with marketplace APIs, OAuth, multi tenancy, billing, and background jobs.
3. A short explanation of how you would assess and productize an existing single shop Node/TypeScript prototype.
4. A production failure or integration problem you diagnosed and fixed.
5. Your availability, preferred engagement model, rate or compensation expectations, and timezone.
If your best work is private, a clear explanation or walkthrough is welcome. Just separate the work you personally owned from your team's.