Know about primary vs secondary indexes? Generally 1 index contains the data, all the other indexes have pointers to that index in their leaf nodes. Usually th

Know about primary vs secondary indexes? Generally 1 index contains the data, all the other indexes have pointers to that index in their leaf nodes. Usually the PK index contains the data So loading 1000 consecutive rows in a created_at secondary index takes two steps: 1) created_at index B-Tree traversal (maybe 10 pages from disk, max?) 2) Potentially loading 1000 randomly sorted pages from disk, dereferencing pointers (EXPENSIVE!) Whereas, if your primary key is sorted by time, loading 1000 rows is 1) slightly larger primary B-Tree traversal 2) no 2, you're done :)