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Performing MySQL schema changes often requires downtime for applications. In this blog, we cover two ways we can perform MySQL schema changes without risking downtime or other MySQL data problems. In this real-life customer example, we perform a schema change to modify the column data type from varchar(20) to varchar(50) on approx. 35 tables from 3GB to 10GB in size. Two of the tables are partitioned, and one of them is about 100GB combining all partitions for that table.

“We don’t take backups, we use replication instead.” If you happen to agree with this statement, I urge you to continue reading. But even if you think you have a good backup plan, I still urge you to continue reading. Taking backups is usually not one of the most exciting parts of the job, but it might be the part that saves your company from a catastrophe. So, let’s make a plan!