When a user signs up to eHarmony they fill out a lengthy questionnaireabout the type of person they are, their likes and dislikes, beliefs, values and preferences in potential partners.\nThe information is fed into the company\u2019s closely guarded, secret algorithm, which serves up the most compatible matches in its user base.\n \nThe matching algorithm is based on data collected from interview with more than 50,000 married couples in 23 different countries, from which the company has derived a mathematical model of a successful relationship it says.\n \nCue butterflies? Not particularly, explains eHarmony VP of technology Prateek Jain.\n \n\u201cSo, I found you the most compatible person on the planet. What if you are not attracted to them?\u201d he says.\n \nIt\u2019s what happens next that counts. Over the last few years eharmony has been leveraging machine learning models and distribution algorithms to boost the butterflies, and help hundreds of users find true love every day. \nThe result is the ultimate recommendations service for singles, the company says, which leads to an average 438 people getting married through the site every day.\n \n\u201cWe say we\u2019re like Netflix,\u201d Jain explains, \u201cbut the movie has to like you back.\u201d\n \nAlgo\u2019 my loving\n \nIn the time before Tinder, telling people you had met your partner online was met with more than a little derision. \nEHarmony, founded by clinical psychologist and Christian theologian Dr Neil Warren and his son-in-law, was launched in 2000, the world\u2019s first algorithm-based dating site.\n \n\u201cI think back in the day when we started I think eHarmony was primarily focused on the compatibility part of its matching algorithms, which was the secret sauce what made it popular,\u201d Jain, who joined the company in 2011 explains.\n \nDespite doubt about the algorithm\u2019s success rate versus other methods \u2013 earlier this year eHarmony ads in the UK claiming its system was \u201cscientifically proven\u201d were banned \u2013 it certainly works for many.\n \nBy 2012, the company had a 14 per cent share of the $2-billion-a-year US dating services industry, according to research firm IBISWorld, boasting 750,000 paid subscribers and 10 million active users.\n \nThe company has a number of regional sites, plus same-sex relationship brand Compatible Partners.\nAustralia is eHarmony's second-largest market by profitability and accounts for about nine per cent of global business revenues.\n\u201cOne thing that became apparent to us was that compatibility was working and doing its job. But we were not seeing a lot of communication happening between the members. We could find you the most compatible person on the planet but if you\u2019re not attracted to them, if you\u2019re not going to reach out to them with a message or call then that match is not going to be success,\u201d he said.\n \nA few years ago, eHarmony started experimenting and investing in big data and machine learning.\n \nIt has since added extra layers to its compatibility system, with around 20 \u2018Affinity\u2019 models at work to ensure the sites recommendations are more personalised and primed for users. Now, matches are based on far more than just the questionnaire; such as how users behave on the site, the profiles they click on and the content of their self-descriptions.\n \n\u201cAll these indirect signals we look for, it allows us to refine the filter,\u201d Jain says.\n \nThe looks, of love\n \nFrom the outset, Jain says, eHarmony\u2019s founders subscribed to the idea that \u201ccompatibility shouldn\u2019t be about looks it should be about personal level compatibility\u201d.\n \nNevertheless, the site\u2019s machine learning models quickly gain an understanding of what you find attractive based on the profiles users interact with.\n \n\u201cWe do not ask any direct questions which ask you to define your attractiveness, but based on what are the kind of matches you are reaching out to we can learn who you find attractive as well as where you rate on the attractiveness score based on how people are reaching out to you,\u201d Jain says.\n \nUsing Google\u2019s Cloud Vision API, user profile pictures are scanned for a number of features \u2013 including hair and eye colour, whether the image shows a beard or moustache as well as \u2018has cleavage\u2019 and \u2018deduced BMI\u2019.\n \nPage Break\nA user that more frequently clicks on blonde-haired user profiles will be served up with more blonde matches.\n \nPreferences are also parsed from written profiles. \u201cSome people mention \u2018I have a thing for guys with beards\u2019 right? If I see that in your profile and can detect in other people\u2019s photos whether they have a beard we can use that as a criteria for matching,\u201d Jain says.\n \nAnother match factor is a user\u2019s site usage. For example, if a user is usually the one to send the first message, they are matched to people who are \u2018shy\u2019 users who rarely do.\n \n\u201cIf you can match those people you can increase the chances of success. Not just for you but the shy individual as well,\u201d Jain says.\n \nAs part of the image analysis, eHarmony is currently working on a tool to help users decide which photos to post on their profile and in which order. Its data has discovered, for example, that photos of individuals wearing sunglasses or in a group don\u2019t do as well. By alerting users when they upload a photo like that, eHarmony will help them maximise the appeal of their profile, Jain says.\n \nOccasionally, the site will serve up a match that is outside your usual preferences, called \u2018Serendipitous Recommendations\u2019. This helps users from \u2018getting caught in a bubble\u2019, Jain says.\n \nClick me maybe\n \nThe front facing systems emit thousands of events. The events are pumped through Apache Kafka and onto Hadoop for processing. Server logs \u201cto figure out where users are clicking\u201d also go into Hadoop and the MapReduce system.\n \n\u201cWe also have traditional data warehouse systems which interact with legacy Oracle systems. We keep historical data back to last 15 years or so,\u201d Jain says.\n \nJain says most of the data sits on premise, however the company is mounting a cloud migration effort, and currently assessing different providers.\n \n\u201cWe\u2019ve realised that we cannot be sitting on sidelines as the industry moves to cloud. Running our own data centres has its own challenges, not just on capital but the time the engineering team is maintaining infrastructure and dealing with vendors and partners if something goes wrong,\u201d Jain, who built eHarmony's spin-off job site Elevated Careers in AWS, says.\n\u201cFor a business of our size I would rather have all my engineering energy focused on new products rather than infrastructure.\u201d\n \nIn this area, eHarmony is playing catch up to its born-in-the-cloud rivals.\n \n\u201cThey don\u2019t have the baggage eHarmony has to maintain years of data. That\u2019s what I\u2019m trying to unshackle us from,\u201d Jain adds.\n \nIt is hoped over the next year, the 100 string technology will ship product multiple times a day, rather than the current multiple times a week.\n \n\u201cThe ultimate vision is: an engineer commits code, it gets picked up by the testing system, it auto runs test cases. If they look good it promotes the code to productions systems and makes it live. If you can cut down this development cycle you can learn your lessons much faster \u2013 rather than working on a feature for months, releasing it and realising people don\u2019t like it,\u201d Jain says.\n \nAn effort is also being made to make the enrolling process far easier on users. This could involve them offering their social media data for eharmony to learn about their likes and dislikes, rather than having to answer questions about them.\n \n\u201cOur barrier to entry is a bit high right now. We would like to be creative around \u2013 how do we ask you all the questions we ask you today and figure out a lot of that without having to ask you explicitly? What can we learn about your personality with some of your social data?\u201d Jain says.