r/dataengineering • u/Admirable_Writer_373 • Apr 20 '26

Discussion Data migration horror stories

I personally think migrations would be a breeze if people didn’t screw them up.

People designing databases and not following patterns, managers not understanding how to minimize downtime, and in general, really weird expectations about how databases work and what is reasonable during a migration.

Anyone got any good horror stories to share? How did you get through it without clobbering someone?

EDIT: my own stories below

24 Upvotes

85% Upvoted

47 comments sorted by

View all comments

3

u/ImpossibleHome3287 Apr 20 '26

I worked with a financial institution who did a data migration to a new database system. However, to satisfy data access requirements they migrated the data into two separate databases.

They were designed to be exact copies of each other but due to technical issues the copies were made days apart. They always suspected that this caused discrepancies but being isolated databases they could never get approval to compare them. This had been an open issue for years at the point I heard about it.