Tenant isolation means one organisation cannot reach another organisation's data through alternate paths. Include background work, file access and caches in the boundary review.
Separate identity from active organisation
In a fictional construction platform, one consultant may belong to two companies. Their personal account does not identify the tenant for every action. Bind requests to an authorised organisation context and handle workspace switching explicitly. A cache keyed without that context can leak information even when database queries are correctly scoped.
Build a negative-test matrix
| Surface | Attempt |
|---|---|
| Project detail | Substitute another company's identifier |
| Search | Query a term unique to a neighbouring tenant |
| Attachment | Reuse a link after access removal |
| Background export | Switch organisations while the job runs |
| Notification | Check both recipient and destination link |
Match architecture to operating constraints
Shared tables, separate schemas and separate databases carry different operational trade-offs. None removes the need for application authorisation. Describe how one tenant can be exported, restored or removed without changing another tenant's records.
Is a tenant filter enough?
It is one part of the design. Review support tooling, scheduled jobs and object storage as well. Useful evidence includes rejected cross-tenant attempts on representative surfaces and an architecture review. This checklist helps scope that work; it is not a complete security assessment or a guarantee that isolation is correct.
Regional operations are not necessarily separate tenants
A multinational customer may want regional teams within one tenant, while independent franchisees require separate boundaries. Clarify the legal and operational relationship with the customer before using geography as a proxy for data ownership.
Sources and further reading
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