SAN FRANCISCO — When Jack Dorsey, then Twitter’s executive chairman, pushed the company to build out its machine learning and artificial intelligence capabilities in 2014, he turned to an engineer, Parag Agrawal.When Mr. Dorsey later became Twitter’s chief executive and needed help overhauling the company’s infrastructure, he also tapped Mr. Agrawal.And when Mr. Dorsey envisioned a future for Twitter in 2019 that would be based on the concept of decentralization and technologies such as the blockchain, he again pulled in Mr. Agrawal to help.On Monday, Mr. Dorsey made the handover complete when he stepped down as chief executive and Mr. Agrawal, 37, was named Twitter’s new leader.Mr. Agrawal, the chief technology officer since 2017, is little known to the public, with even some Twitter insiders saying they were surprised by his appointment. But behind the scenes, the India-born engineer has been a Twitter veteran and confidant of Mr. Dorsey’s who has been involved in many of the company’s big …
