To be honest I'm at a bit of a loss too. My speculation is that since they went all-in on microservices and utilizing various AWS services (something that was underway when I worked there) their data stores have become very much more disparate.

For example, they have the main PostgreSQL data store. Surely that's easy to restore. But the users in that DB have a "foreign key" (in a logical sense, not physical) to the Identity service. This is a real life example that occurred while I was there. So now we have a mixture of multi and single tenancy. So perhaps the identity records are also tied to this app ID and deletes were propagated to that service. And perhaps there is an SQS queue and a serverless function to handle, say, outgoing mail from Jira. Where does this data go? I dunno maybe some Go-powered microservice with its own DocumentDB store. Do deletes propagate here too? Who knows. You can see how this gets complicated and how issues multiply with more services.

Again, this is only speculation. But "decomposing the monolith" was a big deal and it was coming from the top.

Thanks for the insights. It does seem to have, ahem, decomposed.