How Indexing Transformed a Slow Query into a Speed Demon I once optimised a slow-running query by identifying and adding appropriate indexes to the database tables involved. Initially, the query was performing poorly due to full table scans on large datasets. After analysing the execution plan, I added specific indexes on columns used in join and where clauses. This change drastically reduced the query execution time from several minutes to just a few seconds. It was a straightforward yet effective improvement that highlighted the importance of indexing for query performance in data optimisation.