Sitting down for his internship interview at Jane Street Capital in the summer of 2013, the future crypto-billionaire Sam Bankman-Fried was presented with a stack of poker chips and playing cards. But this was no ordinary game.

Jane Street traders, renowned for their financial trading prowess, unveiled an evolving list of quirky rules, peppered with intriguing side bets, as they started to vet the potential recruit.

The aim? To test whether Bankman-Fried had the problem-solving chops to join the secretive, fast-growing and high-speed trading firm that would eventually rival Wall Street behemoths such as Goldman Sachs.

The future FTX boss bagged the internship, was hired full-time and was reportedly paid $300,000 (£230,000) in his first year.

Jane Street, which shuns the limelight, made headlines this week when it emerged that it was advertising New York internships that came with a $250,000 salary. At that rate, the firm’s next crop of interns – particularly those involved in quantitative research and engineering – will be paid more than Keir Starmer, who is paid about £167,000 ($218,000), and the head of the US Federal Reserve, Jerome Powell, who takes home $203,500.

That is also while enjoying breakfast and lunch buffets, mentorship meetings and daily lectures on anything from coding to mock trades and, of course, poker.

But those same highly paid interns do not need a background in markets or finance. Instead, Jane Street is offering the big bucks to graduates with experience in data science, machine learning and coding in order to propel future profits.

But what is Jane Street and how is it able to offer such big cheques to its least experienced recruits?

Jane Street’s beginnings date back to 2000, when it was founded by an ex-IBM developer and a small group of traders in New York. In the decades that followed, it quietly became one of the biggest financial firms that most people have never heard of.

It emerged as part of a new generation of quantitative trading outfits, meaning its traders use mathematics and statistics to determine how to bet on certain assets or financial markets. The company proudly declares itself to be “a firm of puzzle solvers on and off the clock”.

It has particularly become known for its expertise in exchange trading funds (ETFs), which are investment funds made up of a portfolio of assets which are sliced up into shares that can be bought and sold on the market to investors.

That is on top of becoming a major player in equities, bonds and options markets, which have helped push its trading volumes to new heights.

Jane Street is notoriously secretive about its operations. “The first time a New York Times piece appeared about them, there was like a nuclear meltdown,” one former employee told the author Michael Lewis for Going Infinite, his book on the rise and fall of Bankman-Fried.

Part of that may stem from its flat leadership structure, with the firm led by a group of senior managers rather than a single chief executive. Its senior staff are also the equity holders, though only one of its founders, Rob Granieri, remains at the firm.

It has also managed to foster a cult-like dedication from its 2,600-plus employees, who work across its five global offices in New York, Amsterdam, Hong Kong, Singapore and London. The last employs about 636 staff.

Documents leaked to the Financial Times this year showed that Jane Street estimates that it accounted for 10.4% of all stock trading in North America last year and more than 2% of all trading in more than 20 countries.

It reportedly made a 12-month profit of around $7.4bn, meaning it is catching up with well-known titans in US banking including Goldman Sachs, which reported $8.5bn in profits for 2023.

It has helped Jane Street to continue to pay its workforce handsomely. The firm offered pay and benefits worth $2.4bn last year, an average of about $900,000 for each employee.

Between its culture and pay, it seems to have found a winning combination, reportedly keeping staff turnover at just 6% over the last two years.

Jane Street turned down the Guardian’s request for an interview and declined to comment.