This is pretty common in the growth phase of a company, especially one with easily scalable demand such as a software company. As others have pointed out, a lo

This is pretty common in the growth phase of a company, especially one with easily scalable demand such as a software company. As others have pointed out, a lot of projects have been built from 'scratch' due to Twitter's needs and/or culture. This alone has a heavy carrying cost, as they now have the burden of having at least two maintainers for mission critical applications and services. It doesn't mean the engineer-tuples are bijective onto the various projects, but there are only so many tickets a person can resolve. At Amazon, we grew to what we then thought was an insane size in IT (and across the company – we had horrid little offices all over the place in Seattle). This was boosted by a number of acquisitions, such as drugstore.com and homegrocer.com. In 2000, we had a small round of layoffs, then they had another round in 2001. I would expect something similar at Twitter if they don't move horizontally. I would say that, given the competitive HR landscape, it's quite possible they intentionally overhired to secure strong engineers and will rank and yank those who have not turned out to be performers. They're still in an annealing phase, but, honestly, I'm unqualified to speculate on their internal alignment, growth plans, or any RIFs they have planned in the near future.