B2B SaaS platform
Subscription tool, user accounts and permissions, Stripe billing.
Expertise · SaaS
SaaS agency, shipped in 21 days
B2B platform ready to scale. Price set at quote, your code.
You have a B2B SaaS idea: billing platform, marketplace, vertical CRM, business tool. You don't want to spend six months in spec sessions with an agency or get locked into a proprietary no-code tool. We ship your first version in 21 days, live in production, with authentication, Stripe billing, multi-tenant accounts and dedicated hosting. You get the source code. You evolve it after, with us or without.
The package in numbers
21 days
Fixed package
On quote
Price fixed at scope
30 days
Warranty included
100 %
Your code, day 1
3
SaaS shipped in 2026
Q3 2026
2 slots left
§ 01What you get
A B2B platform that runs. Not a Loom demo.
01
A platform live on day 22
Authentication, user accounts, payment, hosting, backups. Plugged into your domain and open to your first clients.
02
Multi-tenant from day 1
Tenant-separated spaces, data isolated in the database. Not a patch added later when you hit 50 users.
03
Stripe included, billing included
Subscriptions, automatic invoices, webhooks, cancellation handling. The piece that takes 8 weeks elsewhere, shipped inside the core package.
04
Your code, your keys, your servers
No proprietary low-code platform holding you hostage. Everything is yours from day 1, handed over at delivery.
§ 02How it goes
From signature to launch, milestone by milestone.
- D 0
Signature
Quote signed. The 21-day clock starts.
- D 1
Onboarding
Access, accounts, final scope confirmed in 2 hours.
- D 7
Client check-in
15 minutes. We show you progress on a product that already runs.
- D 14
Mid-point review
Test on live URL. Feedback integrated within the signed scope.
- D 21
Launch
Production, code handed over, 30-day warranty starts.
§ 03What kind of SaaS
A clear scope per use case.
Vertical CRM
Custom for a sector: real estate, healthcare, education, agencies. Not a generic Salesforce.
Two-sided marketplace
Demand and supply, matchmaking, intermediated payment, commission.
Business platform
HR, finance, ops. Clean workflows, CRM or accounting integrations, dashboards.
Internal tool turned product
You have an internal tool that works. We turn it into a sellable SaaS in 21 days.
Analytics dashboard
Client reporting, proprietary BI sold as white-label, real-time KPIs.
§ 04Three shipped SaaS
From B2B AI to multi-warehouse internal tool.
01 · FeaturedMarch 2026
SouverainIA
AI assistant · B2B SaaS
Digital exec assistant for French SMB leaders. User accounts, 10-day trial, Stripe subscription.
Day 22
Launched
Trial → Pro
Funnel
« Three months stuck with a freelance before 21Day. They shipped a working version in three weeks. »
02April 2026
Ornauto
Internal app · Stock management
Multi-warehouse tool replacing 4 spreadsheets and an Access database. Per-site accounts, granular permissions.
~15 h / wk
Hours saved
5 → 1
Tools replaced
03May 2026
Canoopea
E-commerce · AI platform
AI advisor plugged into 500 PrestaShop products. Without breaking the existing setup.
500
Products
Day 22
Launched
05
For your technical team, if you have oneHow it's built
Production-grade code that you own.
We use technologies that scale to 10,000 users without a rewrite. No proprietary tool, no lock-in. If you take the code in-house, your developers find their bearings in a day.
- Interface
- Next.js + Tailwind. Fast web apps, indexed by Google, multi-language.
- Server
- Node.js + Drizzle ORM. Typed code, testable, ready to scale.
- Data
- PostgreSQL, hosted on Hetzner EU. Daily backups, per-tenant isolation.
- Authentication
- Secure sessions. MFA optional, enterprise SSO on quote.
- Payment
- Stripe. Subscriptions, invoices, webhooks, cancellation handling.
- Hosting
- Vercel or dedicated EU server, your call. CI/CD for deployments.
- Transactional mail
- Resend. Confirmations, magic links, notifications.
§ 06When we're not the right fit
We say no when honesty calls for it.
- B2C SaaS at 10 million users
- Platforms with sub-100ms real-time constraints
- Refactoring a hundreds-of-thousands-of-lines legacy
- Ultra-regulated compliance (health HDS, defence) without audit budget
For everything else, let's talk. We tell you at the first call if we're not the right team.
§ 07SaaS FAQ
Ten questions, ten straight answers.
- 01
- How do you handle multi-tenancy?
- Tenant-separated database, indexed to stay fast at scale. PostgreSQL row-level security if your data is sensitive. The architecture holds from 100 to 10,000 users without a rewrite.
- 02
- Is Stripe included in the package?
- Yes. Subscriptions, automatic invoicing, webhooks and cancellation handling are in the core package. Complex plans (pro-rata, multi-currency, country-specific taxes) are quoted on top.
- 03
- Does my data stay in Europe?
- Default hosting is Hetzner Falkenstein (EU), GDPR-compliant. For France-only hosting we work with Scaleway or OVH, quoted on top.
- 04
- Who owns the code after delivery?
- You do, in full, from day 1. Source code, deployment files, hosting accounts and Stripe access are in your name. No contractual lock-in to 21Day to evolve the product later.
- 05
- Do you integrate with my existing CRM or ERP?
- Yes: HubSpot, Salesforce, Pipedrive, Notion, Airtable, Zapier, n8n and any tool exposing a REST API or webhooks. Standard hookups included in the core package, custom integrations (proprietary ERP, SAP) quoted on top.
- 06
- Is the code ready to scale to 10,000 users?
- Yes. We ship production-grade code: Postgres indexes in place, optimised queries, Redis cache if scope demands. Not a prototype that falls over at 1,000 users. Architecture validated by external technical audits on request.
- 07
- What level of security by default?
- OWASP Top 10 covered by default: password hashing, encrypted sessions, CSRF protection, encrypted backups, hardened hosting. To go further (pentest, SOC 2 certification, ISO compliance), it's an option.
- 08
- What if I want to add a feature after delivery?
- Two options: a new 21-day package for a major block, or a monthly retainer for small evolutions (reserved hours, monthly product review, SLA-backed fixes). Your call, agreed at delivery.
- 09
- How long does the stack you ship last?
- Next.js, PostgreSQL, Stripe: stack choices that hold 5 to 10 years without moving. No ephemeral framework, no proprietary technology. Your developers or another provider take over without a rewrite.
- 10
- Do you build mass-market B2C SaaS too?
- Mostly B2B and B2B2C. For mass-market B2C (10M+ users, viral mechanics, gamified UX), we're not the right team. We'll point you elsewhere.
§ 08Other expertise
When you're ready
Talk about your SaaSYour SaaS live in 21 days.
Tell us about your project in two minutes. Fixed-price quote within 24 hours, live on day 22 if we sign tomorrow.