The c_u index on the action table was defined as (user_id, is_deleted)
without created_unix. The dashboard feed query filters by those two
columns and then orders by created_unix DESC, so the database had to
load and sort every matching row before it could return the first page
of 20 — causing 27+ second queries on large action tables.
Adds created_unix as the third column of the c_u index so the database
can seek to (user_id, is_deleted) and walk created_unix in reverse
order, stopping after 20 rows without a full sort.
Assisted-by: Claude:claude-sonnet-4-6
4405fb0bb7