Hi,
I have recently came to the point when I need to use more then one DB in my usecase.
I had to deal with storing and getting data from multiple DB, based on how old the data is.
I have an archive database to store all logs and data from models to which access will be occasionally.
My application has a customer and contract list, which one per year became obsolete, because of season ends.
Then I move those data to an archive db. However once a while I need to get those data.
Usecase:
DB shardnig would be a great use for me, to save models to DB based on season selected from list (I have a model for that).
If contract belongs to season 2010-2011, save to contracts_2010-2011, else save to contracts_2011-2012.
There is a large number of those contracts (and some of them will not be needed, in next year), therefore having those in one db (counting logs, payments, and django_admin actions and history) is a bad idea.
logs, actions and contracts could be stored in db, based on selection of season.
I hope this description would direct you on what I mean by this question.
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Matt Harasymczuk