What is the zip postcode where Kaitlin lived? | Do you mean the zip postcode in the ares where the staff with first name Kaitlin lived? | Yes
SELECT T1.zip_postcode FROM Addresses AS T1 JOIN Staff AS T2 ON T1.address_id  =  T2.staff_address_id WHERE T2.first_name  =  "Kaitlin"
zip_postcode where Kaitlin lived requires joining Addresses and Staff tables on address_id and staff_address_id respectively; filter condition is Staff.first_name = 'Kaitlin';