What is Unique Constraint vs Index?
A uniqueness guarantee enforced by the database versus a lookup accelerator with no such promise. Postgres implements unique constraints with an index, but only the constraint rejects duplicates.
Related terms
B-Tree Index
The default balanced-tree structure making equality and range lookups fast without scanning every row. Add one where queries filter, join, or sort — then confirm with EXPLAIN before assuming victory.
Composite Index
One index spanning several columns for queries that always filter them together, ordered most-selective first. A three-column composite beats three single-column indexes on the same query shape.
Migration Tracking Table
The ledger recording which migrations already ran, so deploys apply each exactly once in order. Drizzle and Supabase both maintain one; never edit it by hand unless repairing a failed deploy.
Partial Index
An index covering only rows matching a predicate, such as live subscriptions where status is active. Smaller, faster, and cheaper to maintain than indexing rows queries never touch.
Connection Pooling
Reusing a small set of open database connections across many requests instead of dialing fresh each time. Pools cap concurrency, cut handshake latency, and keep serverless bursts from overwhelming Postgres.
PgBouncer & Supavisor
Lightweight proxies that multiplex thousands of app connections onto a handful of real Postgres sessions. Supavisor is Supabase’s managed pooler; PgBouncer is the self-hosted original both patterns descend from.