Actually Im working in a RoR project which must handle more than 10000 requests per day for online data transactions, we have been thinking in mysql but we have doubts about if is enough secure because the sql injections are so popular in this moment (2013), we also think in noSql databases but i found this post:
Is nosql Database good for Online Money Transaction management
it's worring for this part:
I have read in a blog that NoSQL database are not so good for Online Money Transaction i.e. where data integrity is highest importance.( My product has Online money transactions )
Without truly knowing what your product is, it is hard to say whether a NoSQL database would / would not be a good fit. If the primary goal of the product is "Online Money Transaction", then I would suggest against NoSQL database ( at least today in the year of 2011 ). If "Online Money Transaction" is just one of the requirements, but not "the core" of your product, depending on what "the core" is, you can definitely give NoSQL database a try, and for example use an external service to process (e.g. Google Checkout, etc..) your transactions with a guaranteed consistency.
I would like to listen your opinions about which you consider the more appropriate DB for this purpose.