[andreimatei1]

At GitHub they should be using CockroachDB (:P), a scalable relational database that also supports schema changes. Then their FKs would work just fine (albeit with some performance implications).

[hw]

Or, just not use FKs at all. There are many factors to consider when deciding on a DB, and being able to use FKs is probably not high on the list.

[brlewis]

>being able to use FKs is probably not high on the list.

No, that's not at all probable. For many, "database" is synonymous with "ACID database", for which foreign keys are important. https://en.wikipedia.org/wiki/ACID#Consistency