PostgreSQL

Solution

Logical decoding / a publication (Debezium or native), not polling updated_at. Monitor slot lag and disk. A slot nobody consumes is how the primary fills the disk.

Solution

EXPLAIN (ANALYZE, BUFFERS). Name seq scan vs index, then decide. Adding an index without a plan is cargo cult.

Solution

Bloat. Dead tuples, delayed VACUUM, long transactions. Autovacuum is an SLO. “We will warehouse it” does not fix the primary.

Solution

Not for BI. Replica or CDC copy. A federated scan of prod is an outage. Say this even if they did not ask.

Solution

Postgres unique allows multiple NULLs (until NULLS NOT DISTINCT). Warehouse dialects differ. CDC + MERGE on a nullable key silently drops or dupes. Name the constraint.