21Day
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Design × engineering studio

We design, build & ship your product in 21 days

21Day is the product studio for founders and teams who need a real, production-ready product — not slides. Fixed price, full code ownership, 30-day warranty.

Start a project
See our work
  • No scope creep
  • Daily updates
  • You own 100% of the code
21
days, idea to live
100%
code is yours
30
day warranty
21day.io/app/souverainia
On track

Build progress

14/ 21 days
Scope locked
Core architecture
Auth & billing
Dashboard UI
QA & launch

Daily update · Day 14

Stripe subscriptions live in staging
Onboarding flow wired end-to-end
Shipped: team invites + roles
Update posted to your inbox

The modern stack we ship on

Next.jsReactTypeScriptTailwindStripeSupabasePostgreSQLVercelOpenAI
The build, visualized

Scattered parts become a shipped product.

The same way we assemble yours — over 21 focused days.

Why 21Day

Everything that makes builds slip — removed.

Fixed scope, fixed price, and a finish line on the calendar. You always know what's happening and what you'll pay.

Fixed price, upfront

One quote within 24 hours. No hourly billing, no surprise invoices.

You own 100%

Every line of code and asset is yours from day one. No lock-in, ever.

Daily updates

A written update every working day. Watch your product take shape.

30-day warranty

We fix any functional bug free for 30 days after launch.

The 21-day process

From first call to shipped.

Five steps. One fixed timeline. No scope creep.

  1. 1Day 0

    30-minute scoping call

    We map the product, the must-haves, and the edges. No fluff.

  2. 2Within 24h

    Fixed-price quote

    A clear, fixed quote and a start date. You decide.

  3. 3Days 1–21

    We build — in the open

    Parallel, focused development with a written update every day.

  4. 4Review

    Test & iterate

    You review in a real environment. Unlimited iterations within scope.

  5. 5Launch

    Ship to production

    We deploy, hand over 100% of the code, and warranty it for 30 days.

What we build

Production-grade products. Any surface.

One team across design and engineering — so the thing actually ships.

Web apps

Dashboards, SaaS, marketing sites — fast, accessible, SEO-ready.

Mobile apps

iOS & Android from one codebase, store-ready.

Software & SaaS

Auth, billing, multi-tenant — the hard parts, done right.

AI & automation

LLM features and workflows that remove real manual work.

Infrastructure

CI/CD, observability, and cloud that scales without drama.

Product design

UX and UI that looks premium and converts.

Selected work

Shipped in 21 days. Live in production.

A few products we designed, built and launched end-to-end.

All work
SouverainIA
AI assistant2025

An AI executive assistant for French SMBs.

Next.jsLLMAuthStripe
Canoopea
E-commerce AI2025

An AI advisor for pet-retail e-commerce.

RAGE-commerceAutomation
Clinic Booking
Healthcare2024

A booking system for clinics — built in 21 days.

SchedulingNotificationsDashboard
0

days, kickoff to launch

0h

to a fixed quote

0%

of the code is yours

0

day functional warranty