This document summarizes the migration of a 75GB Firebird database from version 1.5 to 2.5 for a pharmaceutical distributor in Russia. Key steps included preparing metadata, testing the data conversion, application migration by checking and updating SQL queries, and optimizing performance. Over 55,000 SQL queries were analyzed, with around 750 requiring changes to work with the new version. The migration was completed in less than 4 months with improved performance on the new platform.