The verdict in three sentences
Moving from one instance per customer to a multi-tenant architecture costs between EUR 15,000 and 35,000 excluding VAT of extra upfront spend in 2026, depending on whether customers are isolated by column or by PostgreSQL schema. The extra cost pays back quickly: infrastructure falls 60 to 80%, and an update ships once instead of thirty times. The real issue is contractual rather than technical: data isolation, backups and per-customer restore must be provable, because they are the first questions B2B buyers ask.
The three isolation models compared
Reference example: a Toulouse software vendor that must serve 30 business customers without duplicating its code.
| Model | Extra upfront cost | Infrastructure for 30 customers | Isolation | Best for |
|---|---|---|---|---|
| Instance per customer (single-tenant) | EUR 0, then EUR 1,500 deployment per customer | about EUR 7,500 per month | maximum | 3 to 5 very demanding enterprise accounts |
| Database per customer | EUR 30,000 to 45,000 | EUR 3,000 to 4,500 per month | very strong | regulated sectors, healthcare, defence |
| PostgreSQL schema per customer | EUR 20,000 to 35,000 | EUR 1,800 to 2,500 per month | strong | 10 to 300 B2B customers |
| Tenant column with row-level security | EUR 15,000 to 25,000 | EUR 1,500 to 2,000 per month | logical, solid if well tested | 50 to several thousand customers |
| Hybrid (column, dedicated database for key accounts) | EUR 25,000 to 40,000 | EUR 2,000 to 3,000 per month | flexible | vendors mixing SMEs and enterprises |
For 30 customers, schema-per-customer and tenant column bring the bill from EUR 7,500 down to EUR 1,500 to 3,000 per month, the 60 to 80% saving stated above. The hybrid model becomes relevant as soon as a customer signs a contract requiring dedicated hosting.
Where the EUR 15,000 to 35,000 goes
| Item | Cost excl. VAT | What you get |
|---|---|---|
| Tenant data model, schemas or row-level security | EUR 4,000 to 9,000 | no query can read another customer's data |
| Multi-organisation authentication, roles, invitations | EUR 3,000 to 6,000 | each customer manages its own users |
| Per-customer backup and restore | EUR 2,000 to 5,000 | restore one customer without touching others |
| Usage-based billing with Stripe Billing | EUR 3,000 to 7,000 | plans, usage meters, automatic invoices |
| Tenant admin console | EUR 2,000 to 5,000 | create, suspend, export a customer's data |
| Automated isolation tests and security review | EUR 1,000 to 3,000 | evidence you can show in customer audits |
| Total | EUR 15,000 to 35,000 |
The line never to cut: isolation tests. A data leak between two customers costs far more than the entire budget, in GDPR breach notifications within 72 h and cancelled contracts.
Usage-based billing: the cost of Stripe Billing
Stripe Billing takes 0.5 to 0.8% of billed revenue, on top of payment fees. For EUR 30,000 of monthly revenue:
| Component | 2026 rate | Estimated monthly cost |
|---|---|---|
| Stripe Billing | 0.5 to 0.8% | EUR 150 to 240 |
| European card payment | 1.5% plus EUR 0.25 | about EUR 458 for 30 invoices |
| SEPA Direct Debit | EUR 0.35 per debit | about EUR 11 for 30 invoices |
| Manual invoicing (for comparison) | 1 to 2 working days per month | EUR 400 to 800 of internal time |
| Automated dunning | included | 1 to 3% of revenue recovered |
Tip: push SEPA Direct Debit with B2B customers; at this volume it costs about 40 times less than cards.
Mini case study
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Sophie, CTO of a Toulouse vendor of aviation maintenance software, serves 30 customers at EUR 1,000 per month. Single-tenant, infrastructure costs EUR 7,500 per month and every release needs 30 deployments. She invests EUR 28,000 in a PostgreSQL schema-per-customer model: infrastructure falls to EUR 2,000 per month, saving EUR 5,500 every month and EUR 66,000 per year. The extra cost pays back in just over 5 months, and Stripe Billing costs her about EUR 210 per month at 0.7%.
FAQ
Does multi-tenancy meet enterprise security requirements?
Yes, if isolation is tested automatically and documented. For the 5 to 10% of customers who demand dedicated hosting, the hybrid model gives them a separate database.
Can an existing SaaS be migrated to multi-tenant?
Yes, allow 8 to 14 weeks and a budget near the top of the range, EUR 30,000 to 35,000, because of the migration of existing data.
How do I restore a single customer's data?
With a schema per customer, restore is direct and takes under an hour. With a tenant column, you need a filtered export designed from the start, i.e. EUR 2,000 to 5,000 of development.
Where should a European B2B SaaS be hosted?
A European provider (OVHcloud, Scaleway, AWS or Azure in an EU region) is enough for most customers. French public-sector buyers may require SecNumCloud qualification, which raises infrastructure costs by 30 to 60%.
Is Stripe Billing essential?
No, but it saves 1 to 2 days of manual invoicing per month from 20 customers. Below 10 customers on fixed plans, simple invoicing is enough.
Let's scope your project. Tell us your customer count, isolation requirements and billing model: we will cost the architecture, the migration and the schedule. Detailed quote within 48 h. WhatsApp +221 77 596 93 33.
Mohamed Bah
Fondateur, Kolonell
Passionate about digital and entrepreneurship in Africa, Mohamed has been helping Sénégalese businesses with their digital transformation since 2020. Founder of Kolonell, he believes every SME deserves a professional and accessible online présence.
