Twitter Inc.'s chief operating officer, Ali Rowghani, has resigned his position, a move that has been linked with slower-than-expected growth the company has seen lately. Rowghani posted on Twitter Thursday morning: "Goodbye Twitter. It's been an amazing ride, and I will cherish the memories." A story published a day earlier on Re/code reported that Twitter was considering an executive shakeup involving Rowghani, given its slow growth, a lack of new product development and the optics created by the sale of 300,000 Twitter shares by Rowghani last month. Citing corporate filings from Twitter, Bloomberg reported on Thursday that Rowghani had resigned his position but would remain a strategic adviser to CEO Dick Costolo, and that the chief operating officer's position would not be filled.