Decision recordMulti-tenant platforms
A schema per tenant: the database owns the name
When every tenant's rows live in a PostgreSQL schema of their own, the mapping from identifier to schema name is a security boundary. So the mapping moved into the database: a stored generated column, a unique index, COLLATE "C", and a plain CREATE SCHEMA as the claim on a new name. With the two error codes that mean 'taken', the one-at-a-time gate, and an EF Core pooling detail that only production-shaped tests found.