I have an app using MongoDB with Atlas Device Sync to save data our data. In the Android App, I have a data model that looks like this:

open class Model(
    // Primary key & irrelevant fields removed

    var page: Int? = 0

) : RealmObject() {
    ...
}

Now, when I save an instance of this object into my DB it will be shown like this (when I query it via the MongoDB Compass app):

{
  "_id": {
    "$oid": "66544dd873f621105bb7a477"
  },
  "page": {
    "$numberLong": "0"
  },
}

Why is the page property saved as a long (Int64) when the Int type for Kotlin is defined as 32 bits? And the Mongo DB Dev Docs also define the Int type as being 32-bit.

The JSON Schema for the Device Sync also defines the property as an Int:

"page": {
  "bsonType": "int"
},

I have the same issue with the iOS app written in Swift. But there, I understand it as the Int data type depends on the device architecture and is actually 64 bits, so it makes sense.