Python is a powerful and flexible ORM with real multi database support. When you are used to gears, you actually get out of the box something like the master lab support. Whenever a needle does only reads, it will be routed to these legs by two of these itself. And that's possible thanks to the SQL alchemy unit of work because at the end of the request, when the unit of work is flushed, you know if it contains only reads or it will contain any change of the documents.