Services · Product Engineering
Full-Stack Product Development
The application around the AI feature
What this is
What full-stack product development covers
Full-stack product development for founders and product teams who need a working application, not only a model: multi-tenant SaaS, internal operations tools, developer APIs, and marketplaces. We build with Next.js, TypeScript, and Postgres to enterprise standards for authentication, tenancy, billing, and observability, and ship the AI features inside the product with the same approval and audit patterns we use for enterprise agents.
Typical timeline: 8–24 weeks
Who hires us for this
- Founders with a validated idea who need a production v1 in a quarter
- Product teams adding a customer-facing AI feature to an existing SaaS
- Enterprises that need an internal tool with proper auth, audit, and tenancy
Problems we get hired for
What usually goes wrong before we are called
The prototype cannot take a second customer
Tenancy, roles, billing, and data isolation are designed in from the start, so the second and fiftieth customer onboard the same way.
The AI feature is a demo bolted onto the UI
Model calls run through the same typed API, with evals, fallbacks, and an approval step where the output matters. Cost per user is known before launch.
No one can see what broke in production
Tracing, error tracking, and audit logs ship in the first release. Support answers come from logs, not from users' screenshots.
How the engagement runs
Steps and the artifact each one produces
- 01
Scope
User flows, data model, integrations, and the one AI feature that matters for v1.
Artifact: Scope document and architecture sketch
- 02
Foundations
Auth, tenancy, billing, CI/CD, and observability in the first two weeks.
Artifact: Deployed skeleton with pipelines
- 03
Build
Weekly releases to a staging environment you can use; AI features behind evals and feature flags.
Artifact: Weekly demos and release notes
- 04
Launch and handover
Production cutover, documentation, and a hiring or retainer plan for what comes next.
Artifact: Runbooks, docs, and handover session
Stack
Tools we reach for
Chosen per engagement against your existing platform. Nothing here is mandatory; everything here has shipped.
| Frontend | Next.js · React · TypeScript · Tailwind CSS |
|---|---|
| Backend | Node.js · tRPC or REST · Postgres · Prisma or Drizzle · Redis |
| Auth and billing | Auth.js or Clerk · Stripe · Row-level security for tenancy |
| AI | Vercel AI SDK · Structured outputs · Approval and audit patterns |
| Ops | Vercel or AWS · GitHub Actions · Sentry · OpenTelemetry |
What you receive
Deliverables
- Scope document and architecture sketch
- Production application with auth, tenancy, and billing
- AI features with evals and approval steps
- CI/CD, monitoring, and error tracking
- Documentation and handover
Proof
Where this has run
Travel & Marine Tech
Harborly: AI-Powered Boat Rental Marketplace
End-to-end marketplace in under 90 days: AI recommendations, dynamic pricing, skipper matching, insurance.
Boat types supported: Manual listings → 6 categories with AI-matched recommendations
Personal Development & EdTech
Navigating Through Time: AI-Driven Guided Journaling
Book to SaaS: 9-week guided programme, multilingual AI chat, live coaching, $50/year membership.
Content delivery: Static book → 9-week interactive programme with progressive access
Banking / FinTech
Conversational Rules Engine for Crypto↔Fiat Banking
Users set salary-day and balance rules in chat; Temporal workflows execute convert → transfer recipes with confirm cards and zero double-pays on webhook retries.
Rule setup time: Support / manual ops → 2–4 min in chat + confirm
Products that ship inside this service
- Xenith Studio · Scaffolding and eval tooling for teams building LLM products.
Engagement models
How we can be hired for this
| Model | Shape | Typical duration |
|---|---|---|
| Fixed-scope build | Defined v1 scope, weekly releases, fixed price with a change process. | 8–16 weeks |
| Embedded pod | One architect plus two to four senior engineers working inside your repos and rituals. | 3–9 months |
| 51-Hour MVP Sprint | Fixed-scope vertical slice to test an idea before committing to a full build. | 51 hours |
Pricing and phase gates are described on How we work.
Questions buyers ask
Frequently asked questions
- How long does a v1 take?
- Eight to sixteen weeks for a multi-tenant SaaS with one AI feature, billing, and auth. Harborly went from architecture to launch in under 90 days. Timelines stretch when integrations or compliance reviews are on the critical path.
- Who owns the code?
- You do, from the first commit. Everything lives in your repositories and cloud accounts; there is no Xenqube platform lock-in.
- Do you build APIs for other developers?
- Yes. Public and partner APIs with versioning, keys, rate limits, and docs are part of this service. Former API development engagements are delivered here.
- What happens after launch?
- Either your team takes over with the runbooks and a handover session, or a retainer covers releases while you hire. We help write the job descriptions.
When this is the wrong fit
- Marketing sites or brochure apps; a design agency is a better fit.
- Projects that need a native mobile app first; we ship web and PWA.
Next step
Send the workflow. We reply with an architecture sketch.
Describe the queue, the system of record, and who signs off today. First brief is free; NDA first if you prefer.