The id functions as an opaque token for use when resuming an interrupted change stream.
OptionalclusterThe timestamp from the oplog entry associated with the event. For events that happened as part of a multi-document transaction, the associated change stream notifications will have the same clusterTime value, namely the time when the transaction was committed. On a sharded cluster, events that occur on different shards can have the same clusterTime but be associated with different transactions or even not be associated with any transaction. To identify events for a single transaction, you can use the combination of lsid and txnNumber in the change stream event document.
For unsharded collections this contains a single field _id.
For sharded collections, this will contain all the components of the shard key
The fullDocument of a replace event represents the document after the insert of the replacement document
OptionalfullContains the pre-image of the modified or deleted document if the pre-image is available for the change event and either 'required' or 'whenAvailable' was specified for the 'fullDocumentBeforeChange' option when creating the change stream. If 'whenAvailable' was specified but the pre-image is unavailable, this will be explicitly set to null.
OptionallsidThe identifier for the session associated with the transaction. Only present if the operation is part of a multi-document transaction.
Namespace the replace event occurred on
Describes the type of operation represented in this change notification
OptionalsplitWhen the change stream's backing aggregation pipeline contains the $changeStreamSplitLargeEvent stage, events larger than 16MB will be split into multiple events and contain the following information about which fragment the current event is.
OptionaltxnThe transaction number. Only present if the operation is part of a multi-document transaction.
NOTE: txnNumber can be a Long if promoteLongs is set to false
See
https://www.mongodb.com/docs/manual/reference/change-events/#replace-event