2.4 Read-only versus Updatable

Another decision is whether a collection should be read-only or updatable (i.e. updates are allowed). Read-only collections are a bit more compact, and have faster indices that preserve document order. Updatable collections, however, have much cheaper index maintenance in the case that new documents are added to a collections. Therefore, even in some read-only use cases, namely those with frequent document additions, it is beneficial to use updatable collections.

Whether a collection is updatable or read-only is decided when it is created (i.e. when the first document is added to it), and cannot be changed after that. However, the backup/restore procedure provides a workaround for this limitation.