It took nine months, but Compass has a new chief technology officer. The SoftBank-backed brokerage said Tuesday that it has tapped Joseph Sirosh — a machine-learning and artificial intelligence expert who’s worked at Microsoft and Amazon — to fill the key role. Sirosh starts today, reporting to Compass COO Maëlle Gavet. Sirosh will be the six-year-old firm’s second chief technologist, following the departure of Liming Zhao, who left to start his own company in March. […]