I am close with some people who worked there until recently. All data access is audited; production access is limited via ACLs in both the main data storage system as well as all the others like the warehouse, realtime ingestion, etc.

FB appears to take this extremely seriously. I just pinged my friends and they said the only way people get fired is for sexual harassment or improper data access. And the second is the one that gets audited and monitored every day.

I imagine at Facebook's scale that nobody has direct access to individual database or application instances; and that if someone actually needed to run queries of any kind in production, it'd be as stringent as deploying a code change.

Pretty strict. You don't get direct db access unless in a very specific team/role. You have to request access to tables on a per-table basis.

I believe this is similar to how Google does it.