I'm making the switch to MongoDB from MySQL. A familiar architecture to me for a very basic users table would have auto-incrementing of the uid. See Mongo's own documentation for this use case.
I'm wondering whether this is the best architectural decision. From a UX standpoint, I like having UIDs as external references, for example in shorter URLs: http://example.com/users/12345
Is there a third way? Someone in IRC Freenode's #mongodb suggested creating a range of IDs and caching them. I'm unsure of how to actually implement that, or whether there's another route I can go. I don't necessarily even need the _id itself to be incremented this way. As long as the users all have a unique numerical uid within the document, I would be happy.
Josh, No auto-increment id in MongoDB and there are good reasons. I would say go with ObjectIds which are unique in the cluster.
You can add auto increment by a sequence collection and using findAndModify to get the next id to use. This will definitely add complexities to your application and may also affect the ability to shard your database.
As long as you can guarantee that your generated ids will be unique, you will be fine. But the headache will be there.
You can look at this post for more info about this question in the dedicated google group for MongoDB:
Hope this helps.
Thanks