One of the problems is that people will give different answers depending on their expertise and there are very few people who have deep knowledge of database development and backend development and supporting large production systems because in the larger enterprise organizations people tend to specialise. I have around 20 years experience using Oracle database and can kind of translate that to other database servers e.g. postgres, sql server etc. I have a bit of knowledge of writing services in c#, ruby or java. Previously I would have advocated putting all the logic into the database but I'm starting to realise some of the compromises involved.

Reading the Oracle or postgres documentation gives a lot of information about the internals, tuning, acid etc although it can be a bit dry...