← Learn/Part 4 · Data engineering

The store has grown, the stock-movement log has thousands of rows — queries are slowing down. Here you learn to see what happens "under the hood" (EXPLAIN) and to speed everything up with the right indexes. The lessons use the stock_movements table (5000 rows): the EXPLAIN tasks simply execute (the plan depends on the DBMS), while index creation is checked through the system catalog pg_indexes.