We automatically backup our SQL DB every day, and keep backups for a month.
NoSQL databases are also backed up, but as it's the aggregated data we create from this that is important (which is saved to SQL and generated pretty much instantly), these are kept only for a week.
Both types of databases are replicated to multiple nodes, so unless an attack is in place that deliberately deletes data (deletion is also replicated), or we mistype a query and write DELETE instead of SELECT, our data is safe. Still, better to be safe than sorry.