In MongoDB, what is the most efficient way to get the first and last document?

To get the first and last document in MongoDB, use aggregate() along with $first and $last respectively. Let us create a collection with documents −

> db.demo73.insertOne({"Name":"Chris"});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5e29c41b71bf0181ecc4226c")
}
.
> db.demo73.insertOne({"Name":"Bob"});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5e29c41e71bf0181ecc4226d")
}
> db.demo73.insertOne({"Name":"David"});
{
   "acknowledged" : true,
   "insertedId" : ObjectId("5e29c42271bf0181ecc4226e")
}

Display all documents from a collection with the help of find() method −

> db.demo73.find();

This will produce the following output −

{ "_id" : ObjectId("5e29c41b71bf0181ecc4226c"), "Name" : "Chris" }
{ "_id" : ObjectId("5e29c41e71bf0181ecc4226d"), "Name" : "Bob" }
{ "_id" : ObjectId("5e29c42271bf0181ecc4226e"), "Name" : "David" }

Following is the way to get the first and last document−

> db.demo73.aggregate({
...    $group: {
...       _id: null,
...       first: { $first: "$$ROOT" },
...       last: { $last: "$$ROOT" }
...    }
... }
... );

This will produce the following output −

{
   "_id" : null, "first" : { "_id" : ObjectId("5e29c41b71bf0181ecc4226c"), "Name" : "Chris" }, "last" : {
      "_id" : ObjectId("5e29c42271bf0181ecc4226e"), "Name" : "David"
   }
}