In Twitter API (https://developer.twitter.com/en/docs/tweets/data-dictionary/overview/tweet-object), some of the fields are Int and some others Integer which are Nullable. For instance retweet_count is Int, but favourite_count is Integer (which is Nullable). What does it mean for favourite_count to be Nullable? and why favourite_count can be Nullable but retweet_count cannot?
I asked a similar question a few years back on the Twitter forum.
For scalability, the Twitter API has eventual consistency. The effect is that sometimes you won't receive all of the data or the data hasn't been updated.
Because of this, some fields are marked as nullable to indicate that there may or may not be data for that field, but we don't know at the time of the query.