Filter audios by feeling

After consideration all pros and cons, I decied:

• Do client side filtering because right now, the number of audios in system is not high, no need complex pagination technique.
• In order to do that, each audio document MUST have a map contains the feeling id. For now, I don't need to show any feeling of each audio anywhere, so I just keep the value is boolean, just for filtering only.

The good thing is no need to do any extra works for querying using where, no need any pagination mechanism, but the performance still good enough.