What is Multi-tenancy? — UK Software Development Guide

4 min readJune 2025ClickMasters Technical TeamReviewed by James Whitmore, CTO
what is multi tenancy saas

Direct Answer

Multi-tenancy is a software architecture where a single instance of an application serves multiple customers ("tenants"), with each tenant's data isolated from the others. This is the defining technical characteristic of SaaS — it allows one codebase and one infrastructure to serve thousands of customers simultaneously and cost-effectively.

Multi-tenancy in the UK

Multi-tenancy has significant UK GDPR implications. Each tenant's personal data must be completely isolated from other tenants — a multi-tenant bug that exposes one tenant's data to another tenant is a UK GDPR personal data breach requiring ICO notification within 72 hours. Three multi-tenancy patterns: shared database/shared schema (row-level security — most cost-effective, highest isolation risk), shared database/separate schema (schema-per-tenant — good balance), and separate database per tenant (maximum isolation — required for regulated sectors like HealthTech). ClickMasters designs multi-tenancy architectures with UK GDPR data isolation as a first-class requirement.

Related Glossary Terms

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