{"slug":"multi-tenant-booking-api-architecture","title":"Multi-Tenant Booking API Architecture: How One Developer Manages Many Businesses","excerpt":"Supporting multiple businesses on one booking API requires data isolation, per-tenant rate limiting, scoped credentials, and subscription enforcement. AvailEngine solves these with Row-Level Security at the Postgres layer, scoped API keys, and a middleware stack that validates rate limits and billing on every request.","date":"June 3, 2026","category":"Engineering","categoryColor":"bg-brand-50 text-brand-700","keywords":"multi-tenant booking system, tenant isolation, row level security bookings","content_html":"<pre>Multi-tenancy is the hardest part of any B2B API. Every tenant needs to feel like they have the whole system to themselves — their data stays theirs, their rate limits don't get eaten by the neighbour, and one tenant going over quota doesn't take down another.\n\nAvailEngine uses **Postgres Row-Level Security (RLS)** as the foundation. Every query is scoped to the requesting tenant's `business_id` at the database level — not in application code where a missed WHERE clause could leak data between customers.\n\nOn top of that, we issue scoped API keys (`avail_live_*` for production, `avail_test_*` for sandbox) that are hashed at rest and resolved to a specific business at request time. Each key carries its own rate-limit counter and subscription tier, so a high-traffic launch won't degrade the experience of the restaurant next door.\n\nThe middleware stack — rate limiting → billing enforcement → usage tracking — runs on every request and fails closed. If a subscription lapses, the API returns **402 Payment Required** before any data is accessed.\n\nDevelopers don't have to think about any of this. One API key, one integration, and the isolation is handled transparently. That's the point.</pre>"}