[glasshug]

Curious why no one else had mentioned this. Are they using online schema transforms besides gh-ost and Percona? Does Postgres handle this better than MySQL?

[golondon]

Postgres has index concurrently which is better or few other instant things which MySQL 8 also has but you still need to be careful.

But some things like adding a column with default value is still hard.

https://www.braintreepayments.com/blog/safe-operations-for-h... this article has a good guideline on this.