[jimminy]

One of the most complex on the front-end was a repaint/reflow issue in Safari that was complicated by the way we were using Angular.

The easiest solution was to use transforms to force rendering through the GPU render pipeline by adding a Z-depth to the elements.

Which caused rendering issues in rendered font-weight for Firefox. We never resolved the issue, even after a root cause analysis showing the bug in Webkit and not Blink or Gecko.

On the backend, it was finding a way to store a persistent collaborative changelog with proper access control and heirarchy on top of a RDBMS. Resorted to redesigning a distributed file-system based on HFS+ and btrfs for COW and COR obligations. This is one of the most data-structure and depth of infrastructural knowledge problems I had to address.