Multi Tenant Data Isolation and Security Questions

Architectural patterns and controls for isolating customer data in multi tenant software as a service platforms. Coverage includes tenancy models such as database per tenant, schema per tenant, and shared schema with row level enforcement, as well as options for separate accounts or projects for stronger isolation. Candidates should discuss trade offs between isolation and operational complexity, how to limit blast radius and mitigate noisy neighbor effects through resource quotas and throttling, tenant aware identity and authorization models, per tenant encryption and key management strategies, tenant aware backup and recovery, data residency and compliance implications, monitoring and alerting for tenant level incidents, secure onboarding and offboarding of tenants, testing and validation of isolation, and migration strategies for moving tenants between isolation models. Also expected are approaches for observability, billing and metering per tenant, data partitioning and indexing for scale, and governance to ensure design meets security and regulatory requirements.