The verdict in three sentences
Multi-tenant (shared database) costs 15 to 30% more upfront but becomes clearly more profitable beyond 20 customers. Single-tenant (one database per customer) reassures on isolation but makes operating costs explode as you grow. The choice is decided by your 24-month customer-count target and your data-isolation requirements.
Single-tenant vs multi-tenant: the comparison
This architecture choice commits your costs for years. Here are 2026 orders of magnitude.
| Criterion | Single-tenant | Multi-tenant |
|---|---|---|
| Initial dev overhead | Baseline | +15-30% |
| Infra cost / customer | High (100-400 EUR/month) | Low (10-60 EUR/month) |
| Data isolation | Maximum | Logical (RLS, schema) |
| Rolling out an update | Per customer | Global, in one go |
| Customer onboarding | Slow (provisioning) | Fast (self-service) |
| Break-even point | < 10 customers | > 20 customers |
| GDPR compliance | Easy to demonstrate | Requires careful RLS |
Below 10 highly demanding customers (banking, health), single-tenant can be justified; beyond 20 standard customers, multi-tenant almost always wins.
Cumulative costs by customer count
The real trade-off reads on the 24-month total cost. Simulation (2026 order of magnitude, infra + operations).
| Customers | Single-tenant / year | Multi-tenant / year | Gap |
|---|---|---|---|
| 5 customers | 18,000 EUR | 22,000 EUR | +4,000 EUR |
| 10 customers | 34,000 EUR | 28,000 EUR | -6,000 EUR |
| 20 customers | 66,000 EUR | 38,000 EUR | -28,000 EUR |
| 50 customers | 160,000 EUR | 62,000 EUR | -98,000 EUR |
| 100 customers | 320,000 EUR | 95,000 EUR | -225,000 EUR |
The tipping point sits around 8-12 customers: beyond that, multi-tenant's initial overhead is absorbed and the gap widens sharply.
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Mini case study
Karim, CTO of a SaaS scale-up in Paris, is undecided for his medical-practice management product. Target: 60 practices in 24 months. Multi-tenant costs +22,000 EUR upfront (RLS, logical isolation, security testing) but brings infra cost down to ~35 EUR/customer/month versus 260 EUR in single-tenant. At 60 customers, annual savings reach ~162,000 EUR. The initial overhead is repaid by the 11th customer; beyond that, each new practice strengthens the advantage. He chooses multi-tenant with Row-Level Security isolation to stay compliant with health-data GDPR.
FAQ
Is multi-tenant less secure for data? No, when well designed: Row-Level Security and schema partitioning guarantee logical isolation. The risk comes from a sloppy implementation, not from the multi-tenant principle itself.
When should you choose single-tenant despite the cost? For heavily regulated customers requiring physical isolation (some banks, sensitive health, defense), or if you target fewer than 10 large accounts. Beyond that, the cost becomes hard to sustain.
Can you start single-tenant then move to multi-tenant? Yes, but the migration is heavy: data-layer re-architecture, isolation testing, data migration. Better to decide early based on your 24-month target.
What upfront overhead should I budget for multi-tenant? Count +15 to 30% on the initial development budget, typically 15,000-40,000 EUR on a v1. This investment pays back by the 8th-12th customer.
Does multi-tenant complicate GDPR compliance? It demands stricter compliance: RLS policies, access logging, per-customer export and deletion procedures. Done right, it remains fully compliant.
Let's scope your project. Give us your 24-month customer target and your isolation requirements: we cost the architecture (single or multi-tenant) and its total cost. 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.
