This article seems to be about really fundamental changes to your data modeling. If you're using MySQL and interested in only changing one table, i.e. adding/removing a column or an index, check out LHM:

https://github.com/soundcloud/lhm

I've used it in the past a lot. You have to make sure to throttle the migration, or else it'll max out your CPU & memory.

Its main advantage seems to be that it doesn't require triggers on the original table (it works by subscribing to the replication log), thus not making write locks worse during the migration.

I haven't tried either yet, so if anybody has some experience with them, do please share a comparison!