Always have year, month, day in filename to easily sort it out.
If file is uploaded by user, add user_id in filename, or some
other unique identifier depends on your business in which you require to
upload.
Personally, I always add timestamp and extra data in filename to avoid duplicate.
Example filename:
yyyy/mm/dd/{user_id}-{timestamp}-{extra}.ext
Be careful with /, too much nested folder is no good for
backup (as they say, idk if true or not, but less folder mean less
complicated to me).