Question

A classical relational database would have a field like USER_ID which would typically be an auto incrementing number. MongoDB has a document id which look something like the following

4f90e98277f6426c0a000001

Can this completely replace USER_ID? I guess what I’m basically asking is, in terms of searching, inserting and indexing is it just as fast as an auto incrementing number? If

Answer 1

It is unlikely that you’ll face performance issues because of primary key being ObjectID rather than an integer. You’ll sooner be affected by data size. I wouldn’t worry about that.

ObjectID brings several benefits:

• it is globally unique (you can create new ids in the application without consulting the database);
• sharding support (no need to synchronize auto-increment sequences between shards);
• monotonically increases with time (and includes actual timestamp, so you don’t have to have separate created_at field if you only want to sort by insertion time);