mongodb objectid

In MongoDB, an ObjectId is a unique identifier that is automatically assigned to each document created in a collection. ObjectId is a 12-byte binary value that consists of a timestamp, a machine identifier, a process identifier, and a counter.

Here's an example ObjectId value:

60db8f75685b0a0a3a3c1d7b

The first four bytes of the ObjectId value represent the timestamp in seconds since the Unix epoch (January 1, 1970). The next three bytes represent the machine identifier, which is usually the MAC address of the machine that created the ObjectId. The next two bytes represent the process identifier, which is a unique identifier for the process that created the ObjectId. Finally, the last three bytes represent a counter value that is incremented for each ObjectId created by the same process in the same second.

ObjectIds are used by MongoDB to uniquely identify documents within a collection. When you insert a new document into a collection, MongoDB will automatically generate a new ObjectId for the document if you do not explicitly provide one. You can also explicitly set the ObjectId value for a document by assigning a new ObjectId value to the _id field.

ObjectIds are generally considered to be unique enough for most use cases, but they are not guaranteed to be globally unique like UUIDs. If you need to generate truly globally unique identifiers in MongoDB, you can use UUIDs instead of ObjectIds.