Anyone know why Facebook moved off HBase? (article doesn't address this)

I get that MyRocks is truly amazing, but I'm wondering what issues they were facing with HBase. I heard HBase was picked over Cassandra (developed at FB) because it was strongly consistent vs Cassandra's eventual consistency.

at the time they picked HBase because it was easier to repair missing replicas. Hdfs namenode juat schedules block replication. Cassandra (at least the version they were considering) had to work a lot harder at replacing a missing replica. Remember they had a version that didn’t have workable merkel trees.

I also heard they had an issue with network flaps causing unrepairable inconsistency. I never got the full scoop on this.

I had worked with the engineers directly responsible for the HBase choice back when. All water under the bridge now it seems.

My guess is operational experience, though the article mentions it was necessary to take advantage of Lightning. I can't think of another business on the planet that has pushed MySQL (and RDBMS' in general) further than FB.

+ app server / schema rework

Have they published a paper on this on Facebook Research?

doesn't really qualify much as research - just lots of engineering to cover all corners

Yes they do/have research. Facebook had 12 papers at the last computer vision conference I attended (CVPR '17) and won the awards for best paper and best student paper.

They have a very strong research arm covering a significant number of research areas. https://research.fb.com/

You are aware that Facebook is the largest website on the planet?