Previously Amazon separated frontend focused engineers (WDE's) and software engineers (SDE's) but the former had a lower payscale than the latter. The end result, every single time, is that great FEE's would simply work at Amazon for 1-2 years and move to Google or Facebook where they were paid considerably more.

Amazon finally rectified it by introducing the FEE role, which has the same pay scale as SDE's. Perhaps more importantly, the WDE role terminated at WDE III and even that was incredibly difficult to achieve.