Long time no posts about databases! So, here’s a short story of how Retool migrated their 4TB Postgres database from version 9.6 to 13.

There are a couple of interesting moments in this story:
- “Lift and shift” migrations are still the case. Sometimes it’s better to have a brief period of downtime than risk a migration to fail mid-way
- Cloud solution might not suit or even fail you. Running things in the cloud doesn’t mean that you don’t need to take care of operations whatsoever (especially when it comes to DBs)
- Test using representative workload be it number of requests or the size of DB.
- Even if there’s a tool for a job, it may require some tweaking. Also, sometimes you need to be creative (it’s in the article, they’ve wrote a script to migrate a pair of particularly large tables)
- Write run books :)

I don’t know, how many of you manage databases, but these points are applicable not only to DB migrations I must say.

#databases