Staying on the SQL theme... The company I work for has a fairly old (~20 years) system. There's a feature for users and site admins to export massive amounts of data, with the option to export data from when the system was first released. Purely CSV or XML data formats. On large datasets, the time for export would vary from 10-20+ hours, and would frequently timeout, forcing you to split exports into multiple timeframes and manually merging them into a single file. The solution? Indexes! Indexes were non-existent. After adding them, export times have dropped to ~10-15 minutes, which is a rather insane performance increase, especially since a single export is accepted per account at a time.