Twitter's stock jumped nearly 30 percent in after-hours trading on Tuesday following the release of its quarterly earnings, as a solid growth in active users soothed concerns about the future of the microblogging site, but some analysts remain skeptical.

As if to downplay the positive impact of the World Cup event on Twitter's second quarter results, CEO Dick Costolo stressed in a CNBC interview that the sporting event – which started on June 12 and went through July 13 – was not behind the pickup in monthly active users (MAUs) last quarter.