How to build race-condition-free invite flows using SvelteKit, Postgres, and Drizzle ORM

A developer has detailed a robust invite-link system built with SvelteKit, Postgres, and Drizzle ORM that eliminates common concurrency bugs seen in production environments. The core fix involves hashing tokens before database storage and performing an atomic delete-then-insert within a single transaction, ensuring only one of two simultaneous clicks on the same link succeeds. Seat-limit checks are executed inside the same transaction as membership creation, closing the gap where a race condition could allow over-enrollment. To prevent overselling invite links at creation time, the system counts both active unclaimed invites and existing members against the seat limit before issuing a new link. Token security is further hardened by using cryptographically random values hashed with scrypt, which is intentionally slow to resist brute-force attacks.