The verdict in three sentences
A startup aiming for 300 customers on a codebase built for 15 must pick its isolation model before writing the first line of version 2. For most B2B SaaS products, row-level isolation enforced in the database offers the best balance of cost, simplicity and security, while schema per tenant is best kept for demanding accounts. A realistic rebuild budget in Berlin sits between 70,000 and 160,000 EUR, part of which can be funded through public programs.
The three isolation models and their cost
Multi-tenancy means serving every customer from the same application. The real question is how data is separated. Three models dominate in 2026, with very different consequences for budget, operations and customer requirements.
| Model | Principle | Indicative rebuild cost | Hosting at 300 customers | For whom |
|---|---|---|---|---|
| Row-level isolation (tenant_id + RLS) | One database, each row tagged by tenant, PostgreSQL security policies | 70,000 to 95,000 EUR | 300 to 900 EUR a month | SME customers, moderate volumes |
| Schema per tenant | One database, one PostgreSQL schema per customer | 85,000 to 125,000 EUR | 700 to 1,600 EUR a month | Customers asking for strong logical separation |
| Database per tenant | One dedicated database per customer | 110,000 to 160,000 EUR | 1,500 to 2,500 EUR a month and more | Health, finance, audited enterprises |
| Hybrid | Row-level by default, dedicated database as a paid option | 95,000 to 145,000 EUR | 600 to 2,000 EUR a month | SaaS selling an Enterprise tier |
| Instance per customer (single-tenant) | A full copy of the app per customer | Cheap at first, costly later | 80 to 250 EUR per customer a month | Avoid beyond 20 customers |
The hybrid model is increasingly popular: 95% of customers share one database, and the 5% of large accounts pay a « dedicated database » option billed 300 to 800 EUR more per month, which more than covers the extra hosting.
What version 2 needs to sell to enterprise accounts
Beyond isolation, IT departments of mid-sized companies ask the same questions in every tender. Answering them at design time avoids losing 20,000 EUR a year contracts.
| Requirement | Development effort | Indicative 2026 cost | Commercial impact |
|---|---|---|---|
| SAML SSO and OpenID Connect | 8 to 15 days | 7,000 to 13,000 EUR | Often a blocker above 200 users |
| Fine-grained roles and permissions | 10 to 20 days | 8,500 to 17,000 EUR | Required by procurement and HR |
| Exportable audit log | 5 to 10 days | 4,300 to 8,500 EUR | Requested by CISOs and auditors |
| EU hosting (Hetzner, IONOS, OVHcloud) | Infrastructure choice | +10 to 25% on hosting | Reassures on sovereignty and GDPR |
| Usage-based billing (Stripe Billing) | 8 to 12 days | 7,000 to 10,000 EUR | Enables per-seat or volume tiers |
| Documented backups and disaster recovery | 4 to 8 days | 3,500 to 7,000 EUR | Standard clause in Enterprise contracts |
On funding, Berlin startups can look at programs such as Pro FIT from IBB, which combines grants and loans for innovation projects, and the federal research allowance (Forschungszulage), which refunds 25% of eligible R&D staff costs. These schemes do not cover everything, but they clearly reduce the net cost.
Typical rebuild schedule
A 95,000 EUR multi-tenant rebuild usually runs over 14 to 20 weeks. Three weeks of scoping and data modeling, eight to twelve weeks of development in two-week sprints, two to three weeks migrating existing customers with parallel runs, then stabilization. Migration is the most underestimated step: every existing customer must find their data intact, tested on a staging environment.
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Lena, CTO of a Berlin startup selling scheduling software to veterinary clinics, serves 15 customers on one instance each, or 15 servers at 120 EUR a month. At 300 customers, that model would cost 36,000 EUR a month in hosting. She chooses row-level isolation with a dedicated database option, for a 98,000 EUR rebuild, of which roughly 24,500 EUR is refunded through the research allowance.
Net cost: about 73,500 EUR. Planned hosting at 300 customers: 1,100 EUR a month instead of 36,000 EUR. The rebuild pays for itself in about two months of operation at full load.
FAQ
Do we have to rewrite everything to go multi-tenant?
Not necessarily. If the code is clean, adding a tenant identifier and database security policies can represent 30 to 50% of a full rewrite, so 35,000 to 70,000 EUR.
Is row-level isolation secure enough?
Yes, if it relies on PostgreSQL Row Level Security and automated tests. It fits 90% of B2B SaaS; plan a dedicated database for customers under health or banking audits.
How much does hosting a 300-customer SaaS cost?
Between 300 and 2,500 EUR a month depending on the model and load, excluding monitoring tools that add 50 to 300 EUR a month.
Is SAML SSO really needed?
As soon as you target companies above 200 employees, it shows up in more than half of tenders. Budget 7,000 to 13,000 EUR to integrate it properly.
Let's scope your project. We design the multi-tenant architecture of your SaaS, its indicative budget and the migration plan for your existing customers. 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.