Goldman Sachs employs about 9,000 engineers in its technology division. That puts the Wall Street firm’s technology team close to the total headcount of some the world’s most valuable internet companies. Facebook employs about 12,690 people globally, Yahoo has roughly 10,400 employees and Twitter has a staff of 3,900.

As at other large banks, however, not all Goldman's engineers spend their time developing new technology. Nearly one third of them spend a lot of their day monitoring the bank's 5,000 critical systems, running tests and looking for problems, according to Don Duet, head of technology, who is based at Goldman Sachs's Wall Street headquarters.