[kokey]

I spent some time last year at a bank setting up an Oracle DB that would replicate data from MongoDB, for reporting. The Oracle DB, once set up right, was considerably faster with the queries we wanted than MongoDB, and that was in between running massive imports. MongoDB was running on 6 big physical boxes with loads of RAM, while Oracle DB was only running on a single virtual machine using 16GB of RAM. The reason this worked was because of the wealth of Oracle knowledge out there, access to experienced DBAs with knowledge of good methods, etc. I found MongoDB to be a bit young in this sense, performance tips were down to 'change your schema' which is also true for Oracle but there are many ways to make Oracle work better with a legacy bad schema. That said Cassandra, MongoDB etc. seems to be taken up by the banks at a rapid pace, mainly for analysis tools e.g. in trading.