Unused index — wasted write overhead

What it is

The advisor reports an index the query planner never uses.

Why it matters

Every insert, update, and delete maintains it for no read benefit, so it is a write tax and disk usage with nothing on the other side of the ledger.

How to fix it

Drop it: DROP INDEX CONCURRENTLY IF EXISTS schema.index_name;. CONCURRENTLY cannot run inside a transaction block, so put it in its own migration file. This is reversible — recreate the index if a future query needs it — so it is one of the safer cleanups available.