Today, PlanetScale announced support for foreign key constraints. This has been in the making for quite a while — around a year in fact. So, what was the problem? Why did it take so long? It’s something that any and every database supports, right? Yes and no. To support foreign key constraints is one thing. To do so while still delivering Online DDL, gated deployments, online imports, and eventual
![The challenges of supporting foreign key constraints — PlanetScale](https://cdn-ak-scissors.b.st-hatena.com/image/square/4f45d05d4814ebf0b6103d860e1fc6d9bb80cc27/height=288;version=1;width=512/https%3A%2F%2Fplanetscale.com%2Fassets%2Fblog%2Fcontent%2Fchallenges-of-supporting-foreign-key-constraints%2Fforeign-keys-shlomi-social.png)