How Fast are Engineers at companies like Google, Facebook, Amazon, etc.?

This question may be a bit off-topic, but I have always wondered how fast are engineers working at top companies like Google, Facebook, Amazon, etc.

For example, if you told them to implement a new Convolutional Neural Network recently published in a conference. How long would they take to a create a high-quality Github repository along with a detailed analysis for a case study? (using an existing library like TensorFlow)