In the not-too-distant future of Nosedive - the episode that opens Season 3 of Black Mirror, a science-fiction anthology series - social-media rankings determine one's access to everything from housing to healthcare. A low score can even land a person in jail.

This dystopian vision is not that much of a stretch given the current obsession with online ratings, say the episode's stars Bryce Dallas Howard and Alice Eve.

"That's why this world feels like it's happening already," says Howard, who appeared earlier this year in the adventure movie, Pete's Dragon. "Very quickly, we're getting to more and more systems where people are rating one another with likes and whatnot. Airbnb, Yelp, Uber - it's everywhere.

"All it takes is someone officially saying, 'Let's really have this rating thing be a part of society', and we're there and Nosedive is happening."

So while things are not quite as extreme as they are in the episode, "where if you're below a 2.5, you lose your job", there are already "consequences where, if you say the wrong thing (online), you could lose your job", she continues.

She and Eve spoke to The Straits Times and other press in New York about the acclaimed show, which recently unveiled its new season on Netflix.

Both actresses admit that they themselves have fretted over what they share on social media and have had to take pains to keep their public and private lives separate.

Howard, 35, joined Facebook only late last year, after she was encouraged to do so by her father, the Oscar-winning director Ron Howard (A Beautiful Mind, 2001), who she says is an early adopter when it comes to such technologies.

Just a few weeks later, however, she felt she "definitely could have gone to the dark side in terms of the anxiety and pressure around social media".

"It's so stressful," she says, revealing that she is also the sort of person who worries about making spelling and grammatical mistakes in posts.

Eve, 34, had concerns as well. "I have a thing that I'm learning my way out of, which is saying what I think. That's dangerous on social media - saying what is your truth and saying the thing that comes to mind. So I didn't ever join Twitter because I thought that might be dangerous.

"And then, I did join Instagram, but via my friend who knows me very well and kind of segued me into the platform and taught me that it's basically a cartoon world and you don't tell the truth.

"And now, I know and I've got the hang of it and I'm not my authentic self. That's the best way to be," says the British star, who is married to financier Alex Cowper-Smith, 34, and appeared in Star Trek Into Darkness (2013).

In Nosedive, Howard plays Lacie, a woman consumed with improving her falling social-media score. Eve is her childhood friend Naomie, a high scorer whose picture-perfect life Lacie wants to emulate.

But the actresses point out that not everything is as it seems with the Naomies of this world.

Observes Howard: "Nosedive is a satire of that sort of Instagram world that's always presentable and always aesthetically sophisticated."

Eve adds: "The complication is when we believe that it's the same as the real universe, but it's just not."

They say they have had to learn to guard their privacy while maintaining a social-media presence - something many celebrities feel pressured to do in order to boost their profile, Eve says.

"The truth is, we're probably quite quiet on our own at home - and that wouldn't work, really. There's an element of you having to put on a public face, otherwise you're just a potato."

Both women try to keep their posts fun and light-hearted. Eve likes the messaging app, Snapchat, in which users can add silly filters to pictures, "because it cartoonifies you and it kind of leans into that idea".

"Leaning into the imagined universe is the most healthy way we can approach it," she says.

She and Howard also take the extra precaution of never putting anything up too quickly and rarely share images taken on film or TV sets because it would feel inappropriate.

Howard says: "I very rarely am, like, 'I just want to post that', and post it within 15 seconds. It takes some time."

Chatting to reporters in Los Angeles earlier this year, Black Mirror creator Charlie Brooker says Nosedive is "a satire about identity in the social-media age - it's kind of like a cheerful pastel nightmare" about the dark side of social networking.

Black Mirror, a Twilight Zone- like series, gained a cult following after its British debut in 2011 and has now been picked up by Netflix. Other episodes explore additional aspects of techno-paranoia to do with gaming, virtual reality and the lack of privacy in the digital age.

Brooker, a 45-year-old former video-game journalist, says he is not anti-technology in any way.Nor is his show.

"Technology is never the villain in this show. It's always about the human failings and human messes that technology has helped facilitate."

But while he goes on to insist the series is not trying to be didactic, Howard intends to use Lacie's hellish experiences in Nosedive as a sort of cautionary tale for her children.

The actress, who has two kids with actor husband Seth Gabel, 35, says they are not on social media yet because "they're way too young now".

"My son is almost 10, my daughter is almost five, and they don't know what (social media) is, as far as I know - which is cool. But I am going to show them this episode before I allow them to join social media. When I saw this, I was like, 'Yes, just what I need - them seeing their mother go through this.'"

•All three seasons of Black Mirror are available on Netflix.