Insights · Article · Engineering · Apr 25, 2026
Shared database isolation, session context, migration hazards, and escape hatches when a few tenants need dedicated infrastructure without forking your codebase.
Row level security promises cheaper operations than siloed databases per tenant. It demands relentless tenant_id discipline, secure session context binding, and tests that prove cross-tenant reads cannot occur.
Standardize tenant resolution at authentication: JWT claims, session variables, or connection pool hooks. Every query path must set context before hitting pooled connections.
Administrative and support tools are high risk. Impersonation features need logging, approvals, and time limits. One forgotten impersonation session is a headline.
Migrations must backfill tenant columns and verify constraints before enabling policies. Partial migrations create silent holes.
Performance tuning changes with RLS. Indexes should align with tenant-scoped queries. Explain plans under tenant context differ from superuser previews.
Large tenants may eventually need dedicated shards. Design portability layers so code paths do not multiply uncontrollably when you graduate whales.
Backup and restore drills should include tenant-scoped restore tests. Regulatory customers will ask whether another tenant’s restore can leak into their environment.
Document escape hatches for break-glass support with legal sign-off. Absolute rules without documented exceptions invite shadow databases.
Finally, automate integration tests that attempt cross-tenant access with malicious session swaps. Passing once at launch is insufficient; run in CI continuously.
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