While Twitter has not confirmed the news itself, the company has apparently acquired Ubalo, a "scalable computation" startup.
The news appears to have been broken by TechCrunch, and Ubalo has posted the following message on its homepage:
We’ve got some exciting news: The Ubalo team is joining Twitter. In early 2011, we started Ubalo to make large-scale computing easier and more accessible to a technical audience, and we’ve had a great time working with our partners and customers on a number of interesting products. When we met the infrastructure folks at Twitter, we realized that it’s a company with brilliant people, strong momentum, exciting challenges and a promising future. We quickly became enthusiastic about the possibility of collaborating with them and the impact we could have there.
A few days ago, Twitter agreed to acquire our technology and we agreed to join their staff. We look forward to working with Twitter in the years to come.
Thanks for your support and interest in Ubalo!
TechCrunch says Twitter declined to "officially" comment on the deal.
We've got some exciting news: The Ubalo team is joining Twitter. Read more: ubalo.com.
— Ubalo, Inc. (@ubalo) May 9, 2013