Tenant Isolation

A tenant is an organization or group served within a shared system. Tenant isolation prevents one tenant's requests from accessing another tenant's resources outside an explicit authorized arrangement. Sharing infrastructure does not require sharing data access.

An identifier is not evidence of membership

Suppose a user from shop A supplies shop B's identifier in a URL. The service must derive membership from verified identity and check the requested resource. Trusting the supplied identifier would let the request choose its own security boundary.

Apply the boundary to queries, files, background jobs, search results, and caches. An answer cached for shop A must not reach shop B just because the question matches.

Isolation has more than one layer

Data-access isolation differs from limiting competition for processors or memory. Both can matter, but a separate compute queue does not establish authorization. Test cross-tenant requests as well as different users inside the same tenant; tenant membership alone may not permit every record.

Reference: OWASP Authorization.