Multi-tenancy
Multi-tenancy is a software architecture in which a single platform serves many separate customers ("tenants") from shared infrastructure, while keeping each tenant's data and configuration isolated from the others.
What it means. In a multi-tenant system, many organisations use the same underlying software and infrastructure, but each operates in its own logically separated space — its own data, users, settings and branding — with strict isolation so no tenant can see or affect another. It contrasts with single-tenancy, where each customer runs a separate, dedicated instance of the software. The tenants share the machinery but never the data, which is the defining balance the architecture has to strike.
Why it's used. Multi-tenancy is the architecture behind most modern software-as-a-service. Sharing infrastructure across many tenants makes the platform far more efficient to run and update: improvements and fixes reach everyone at once, and capacity is used efficiently rather than duplicated per customer. The engineering challenge — and the mark of a well-built multi-tenant platform — is keeping tenants rigorously isolated so that shared infrastructure never means shared data, even under failure or misconfiguration. Get isolation wrong and the efficiency is worthless; get it right and one platform can serve thousands of customers reliably.
Where it fits. In financial services, multi-tenancy underpins platforms that serve many businesses at once — including Banking-as-a-Service providers, which run many partners' offerings on shared, isolated infrastructure. Strong tenant isolation is especially important here, because the data involved is sensitive and regulated, and a leak between tenants would be a serious breach. It is closely related to how white-label and BaaS platforms are built and scaled, and it is what makes it economically viable to offer regulated financial capability to many partners at once.