Originally designed to be produced as a feature-length film, until Netflix stepped in and turned it into a three-part mini-series. The total runtime, however, is 135 minutes, which isn't much more than that of the average single feature film.
The trivia items below may give away important plot points.
In the room with 5 prisoners and Nida, when we learn that the ghoul is one among them. Nida quickly concludes it's not Ahmad and asks him to stick to her. Rajjan falls down and says he knows who the Ghoul is, this is because when the story of how Ahmad lost his voice is narrated, the Maulvi says that captain had brought Ahmad's wife and child in the isolation room alone and then killed them in front of Ahmad who then lost his voice. He couldn't have know it from Ahmad since he lost his voice and the captain wouldn't have personally told the Maulvi, only the Ghoul could have known this since he sensed the captain's guilt earlier on in the isolation room. Rajjan realises this but is soon killed. Nida sees Ahmad shed tears holding his son's torn T-shirt and knows those are emotions, peculiar to humans and not the Ghoul.
In the third episode, when Nida asks one of the soldiers to pick out the tape recording of her father, one can see the date of recording as 08/08/2019. She says it was recorded few weeks ago, which proves the series is based sometime in July/Aug 2019.
In spite of being set in the future, Ghoul features cars and gadgets from the past, such as the Maruti Esteem and a Nokia 3310 mobile phone. Present emission norms wouldn't allow the Maruti Suzuki Esteem to continue playing on the roads, while the 2G spectrum used by even the updated Nokia 3310 would most likely not be available either.