The verdict in three sentences
For an Amsterdam vendor growing from 5 to 80 customers, a shared database with Row Level Security (RLS) offers the best balance of cost, simplicity and scalability, with infrastructure around EUR 300 to 800 a month. Schema per tenant or database per tenant only make sense for enterprise customers demanding physical isolation, data residency or dedicated encryption, and push infrastructure towards EUR 1,500 to 3,000 a month. Rebuilding into a clean multi-tenant architecture costs EUR 30,000 to 70,000 excluding VAT and should happen before customer 20, not after customer 60.
The three isolation models compared
The CTO must trade off running cost, security as perceived by customers and migration complexity. Each model has a threshold where it becomes painful.
| Criterion | Shared DB + RLS | Schema per tenant | Database per tenant |
|---|---|---|---|
| Infrastructure for 80 customers | EUR 300 to 800 a month | EUR 600 to 1,500 a month | EUR 1,500 to 3,000 a month |
| Schema migrations | Single run | 80 orchestrated runs | 80 databases to migrate |
| Isolation as seen by an enterprise | Logical, must be documented | Good | Maximum |
| Onboarding a new customer | A few seconds | 1 to 5 automated minutes | 5 to 30 automated minutes |
| Cross-tenant leak risk | Low if RLS is tested | Very low | Near zero |
| Backup and restore of one tenant | Complex, by filter | Simple, by schema | Very simple |
| Practical limit | Several thousand tenants | A few hundred | Tens to a few hundred |
A hybrid model is often the answer: shared database with RLS for most customers, a dedicated database sold as a premium option to the 3 to 5 enterprise accounts that require it.
The multi-tenant rebuild budget
Moving from a single-customer application to a multi-tenant platform touches authentication, data, billing and operations. Typical lines for an Amsterdam vendor:
| Line | Scope | Indicative 2026 budget (excl. VAT) |
|---|---|---|
| Audit and design | Data mapping, model choice, migration plan | EUR 4,000 to 8,000 |
| Data model and RLS | Adding tenant_id, RLS policies, automated isolation tests | EUR 8,000 to 18,000 |
| Authentication and roles | SAML/OIDC SSO for enterprises, roles per organisation | EUR 5,000 to 12,000 |
| Provisioning and billing | Automatic tenant creation, plans, limits, Stripe | EUR 5,000 to 12,000 |
| Dedicated database option | Per-tenant routing, multi-database migrations | EUR 4,000 to 10,000 |
| Observability and backups | Per-tenant logs, metrics, targeted restore | EUR 2,000 to 5,000 |
| Migrating existing customers | Moving the first 5 customers with no downtime | EUR 2,000 to 5,000 |
A rebuild focused on the shared database alone fits in EUR 30,000 to 45,000. With SSO, a dedicated database option and full observability, it reaches EUR 55,000 to 70,000.
Enterprise requirements and GDPR
Procurement and security teams at large Dutch and European companies send security questionnaires of 100 to 300 questions. Recurring points: EU hosting, encryption at rest and in transit, access logging, SSO, exit plan and retention periods. GDPR requires a data processing agreement (Article 28), a record of processing and the ability to export or delete one customer's data. Some sectors expect ISO 27001 certification, and Dutch healthcare customers often ask for NEN 7510, which pushes towards a dedicated database for those accounts.
Mini case study
Need a professional website?
Kolonell builds websites that attract clients, optimized for the Sénégalese market. Free quote in 2 minutes.
Daan, CTO of an HR SaaS vendor in Amsterdam, serves 5 customers on a duplicated single-tenant setup. Each new customer costs him 3 days of installation, about EUR 1,800, and every release is deployed 5 times. At 80 customers that would mean EUR 144,000 of onboarding and unmanageable releases. He invests EUR 50,000 in a shared database with RLS, SSO and a dedicated database option sold at EUR 400 a month extra. With 4 enterprise customers on the option he collects an extra EUR 19,200 a year, and infrastructure moves from 5 servers to one platform at EUR 700 a month. The rebuild pays for itself before customer 25.
FAQ
Which multi-tenant model should a B2B SaaS choose in 2026?
A shared database with RLS suits most vendors up to several thousand customers, for EUR 300 to 800 a month of infrastructure. Add a dedicated database option for enterprise customers who demand it.
Is RLS secure enough?
Yes if policies are tested automatically on every deployment and the application never bypasses RLS with a superuser account. A suite of 50 to 100 isolation tests takes a few days to build and reassures auditors.
How much does rebuilding a single-tenant application cost?
Between EUR 30,000 and 70,000 excluding VAT depending on SSO, the dedicated database option and billing. Typical timeline is 2 to 4 months.
How do we meet customers' GDPR requirements?
EU hosting, an Article 28 processing agreement, a record of processing, encryption, and export or deletion of a customer's data within 30 days. The architecture must support these operations per tenant.
Should dedicated isolation be charged?
Yes, a dedicated database costs EUR 150 to 400 a month in infrastructure and operations. Most vendors sell it as a premium option at EUR 300 to 800 a month.
Let's scope your project. Share your current customer count, your 24-month target and your enterprise requirements: we will price a multi-tenant rebuild between EUR 30,000 and 70,000 with a zero-downtime migration plan. 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.
