Currently we do not have any clear constraints set for the query performance over large database. It is expected to have a small delay of the crud operation along with the increasing number of items in your tables.
Basically the structure of your tables and the type of queries are the main thing to consider.
To be more specific the create operations might not be affected as much as the other operations - read and update queries, which depend on the number of items in the table. By default there are no indexes created on any field. This means that if you have a set of such operations, they can be additionally optimized by creating an index depending on the type of query. We can assist with this as soon as you experience any slowness of your queries. The delete operations also depend on the type of filter that you provide.
Hope this information will help you.