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Expertise · Custom applications

Your applications, designed, custom-built

From scoping to launch. Modern stack (Next.js, TypeScript, Supabase, PostgreSQL) with AI integrated only when it delivers measurable value.

app.sitex.com / commandes
v2.4.1
Orders · week 21
2 384
+12% vs S20
IDClientStatusAmount
#10428Loiret SAEn cours1 240 €
#10427BellmanLivré 860 €
#10426CabaiaLivré2 110 €
#10425Art ExploraEn attente 540 €
01 — Why us

One team.
From scoping to delivery.

Three concrete commitments that shape how we deliver, from the first workshop to production deployment.

01

One team, from the first workshop to support

Scoping, design, development, deployment. The developer who engages with your business team during scoping is the one who writes the code.

02

Production-grade code, not a disguised AI prototype

AI speeds up our prototyping, but what goes into production is reviewed, tested, monitored, and maintainable code for your teams.

03

Modern stack, technical debt under control

Next.js, strict TypeScript, PostgreSQL, automated tests, human oversight, and end-to-end validation.

02 — Areas of intervention

Four application families.
One dedicated page per use case.

Four formats we design and deliver regularly. Click to explore our approaches, client cases, and the tailored method for each.

Looking for an editorial site or a multi-country CMS? View Websites & CMS.

05 — Other case

Have another application idea? Let’s discuss. A single conversation is enough to assess the project and outline next steps.

Book a call
03 — Tech stack

A modern stack
for custom applications.

We tailor our stack to the client context (sovereignty, GDPR, existing in-house teams, SI integrations).

01

Front

Next.jsReactTypeScript
02

Back / Data

03

AI / Agents

04

Auth (SSO)

05

Testing

VitestPlaywright
06

Ops / Hosting

OVHScalewayDockerVercel
07

Monitoring

SentryPostHog
08

CI / CD

GitHub Actions
Each stack choice is discussed during scoping to meet your needs—never imposed by default.
04 — Client case · SiteX

From Airtable to a custom application.

Gradual migration to Next.js + Supabase, with the old system coexisting until full switch. Zero business disruption.

Read the case study
SaaS · Security2024 — 2026 · 24 months

Sitex

Business application for event security service planning, with on-site tracking and real-time incident reporting.

100 %of on-site incidents tracked via QR code reports
+65 %time saved on administrative tasks for document management, imports/exports, and event tracking
2xmore operational visibility for internal teams thanks to the dashboard and real-time tracking.
Next.jsSupabase
05 — Method

A project

No handoffs between scoping, build, and run. The same engineers support you from the first workshop to maintenance, so knowledge isn’t lost along the way.

01Scoping1 to 3 weeks

Spec, plan, estimate.

Business workshop, use case mapping, constraints (IT systems, GDPR, security), quantified success criteria. Deliverable: functional spec + technical plan + fixed estimate.

02Design produit2 à 4 semaines

Parcours validés.

Wireframes, user journeys, design system, mockups. Full validation before any code is written.

03Build itératif2 à 6 mois

Sprints de 2 semaines.

Demo at the end of each sprint. Your IT teams involved from sprint 1 — code reviews, pair programming if requested.

04Mise en prod1 à 2 semaines

Bascule sécurisée.

Load testing, security audit, rollout plan, team training. No Go Live without measurable quality criteria.

05Run & évolutionsContinu

Maintenance ou transfert.

Corrective maintenance, updates, gradual handover to internal teams if desired. Our goal is not to become indispensable to your operations.

06 — Questions

Frequently asked questions

The questions we hear most often during scoping. If yours isn’t here, get in touch!

Default stack: Next.js + Supabase + TypeScript. We adapt if you have an existing setup (Python, Go, Java) or specific infrastructure constraints. The stack is chosen during scoping, based on the actual context.

No. AI is one tool among others. We integrate it when it delivers measurable value: internal assistant, RAG, automation agent. Not to tick a marketing box.

If desired, yes. Co-construction from scoping, code reviews, documentation, training. Knowledge transfer is part of the scope.

Yes, on OVH, Scaleway, or self-hosted. Depending on data sensitivity (healthcare, defense, finance), we adapt the architecture.

Optional maintenance contract (SLA, on-call, updates) or full handover to your team with documentation and training. No technical lock-in—our goal isn’t to become indispensable to your operations.

Yes, it’s one of our core services. Independent audit in 1 to 2 weeks, diagnosis, and a recovery plan.
Get started

An idea, a business need, or an existing project to take over?

Contact details
20 Rue des Taillandiers
75011 Paris
Response within 24 business hours.