Diagnostics and safe rollout checklist

Before shipping a user-facing serving query:

Write the exact query shape.
Create the primary key, access path, hybrid descriptor, rollup, or bounded join path that should drive it.
Wait for queryability.
Run EXPLAIN (FORMAT JSON) ADMIT.
Verify selected driver, pushed filters, residual verification, candidate budget, ordering/ranking contract, page identity, and owner-aware routing evidence.
Run ADVISE if the query refuses or reports weak evidence.
Treat typed refusal as a safety feature, not a missing catch-all scan path.

Useful stable refusal codes include unsupported-shape, missing-index-family, insufficient-index-order, range-budget-unproven, capability-not-queryable, conflicting-order-contract, over-budget-tablet-fanout, over-budget-candidate-fanout, over-budget-verification, continuation-drift, and schema-generation-incompatible.