Mr. Poirier, 32, a New Hampshire native who started a coding business at 14 before heading to Columbia University, worked on analyzing fixed-income products at Lehman Brothers from 2003 to 2006, before that Wall Street firm collapsed from mismanagement of its own risk. “Trying to figure out a yield, I’d work with a dozen different computer systems, with different interactions that people didn’t understand well,” he said.

He then took a job with Palantir Technologies, a company founded to enable military and intelligence agencies to make sense of disparate and incomplete data. He went on to build out Palantir’s commercial business, managing risk for things like JPMorgan Chase’s portfolio of subprime mortgages.

There were plenty of parallels between the two worlds, but instead of agencies, spies and eavesdropping satellites, finance has markets, investment advisers and portfolios. Both worlds are full of custom software, making each analysis of a data set unique. It is hard to get a single picture of anything like the truth.

Even a simple question like “How many shares of Apple do I own?” can be complicated, if some shares are held outright, some are inside a venture fund where the wealthy person is an investor and some are locked up in a company that Apple acquired.

Finance “was the same curve I encountered in the intelligence community,” Mr. Poirier said. “How do you make sense of diverse information from diverse sources, when the answer depends on who is asking the question?”

The parallel was also evident to Mr. Lonsdale, a Palantir co-founder. From an earlier stint at PayPal, he had millions in cash and on paper is a billionaire from his Palantir holdings. He also knew lots of other young people in tech who could not make sense of what was happening to their money. “Wealth management is designed for the 1950s, not this century,” he said.

Mr. Lonsdale left Palantir in 2009, starting Addepar with Jason Mirra, another Palantir employee, in 2009. “It didn’t make sense for Palantir to hire 20 or 30 people to work in an area like this,” Mr. Lonsdale said. Mr. Mirra is Addepar’s chief technical officer. Mr. Poirier joined in early 2013 and became chief executive later that year.