That isn't efficient since the Collection is being accessed twice instead of once. It's also not 100% effective. Between the time of reading and adding, a record could be added with the same key.

All that Appery.io has appeared to support is Non-Unique Single Field indexes. How about Compound Indexes, and specifying Unique?
http://docs.mongodb.org/manual/core/i...
http://docs.mongodb.org/manual/core/i...

MongoDB supports indexes - http://docs.mongodb.org/manual/indexes/. It would be nice if the Collections Maintenance UI allowed indexes to be defined and maintained.

If I create an e-mail address column, and I want the column to be unique, how do I specify that?

Can I specify the value of the _id column, instead of using the value that is automatically generated?

How do I create a unique index on a Collection to prevent duplicates, and a non unique index on a Collection to improve search performance?