@rocio.ortiz said:

• Calling the "Changes" API (https://api.themoviedb.org/3/movie/changes) and to get the new IDs, and then get the genres of those IDs. However with this approach I'm not sure that the IDs from the new movies are also included, or if it's just the IDs from the movies that were present already but had information changes.

The creation of a new movie is a change.

• The other possibility is using the "Latest" API (https://api.themoviedb.org/3/movie/latest) to get the IDs movies that were added, which seems perfect but there is no information on how far back it's looking (is it the movies that were added in the last week, month or year?)

How far it is looking is irrelevant, as it give you only one single Id : the last one that have been created in the database.

Just an idea.
Maybe a better solution would be to download the list of valid movie IDs.
https://developer.themoviedb.org/docs/daily-id-exports
http://files.tmdb.org/p/exports/movie_ids_10_03_2024.json.gz
It is basically in ascending order.
There are about 5 or 6 movies at the beginning that are out of order.
Every new movie gets an ID in this ascending order.

The ID of a Movie deleted from our Database is an ID that will never be reused.

So, check your Database for the largest ID.
And in the list of valid IDs, all IDs greater than your largest will be the new IDs.

Thank you, both! @ticao2 your approach makes perfect sense and is probably the way to go for the application I'm thinking, will give it a shot!