Earlier quoted context omitted.
Exactly. It's not exactly computationally expensive if you can do it at 2GB/s! https://news.ycombinator.com/item?id=26931581
it's computationally expensive if it's more computation than all the other things you'd like your hardware to do, i think is a better definition.
The author seemed to have parsed the protobuf data by converting it all to a huge hierarchy of thousands (millions?) of Python objects. Of course that is slow and takes a few seconds. That's so many allocations!
But if you are just looking for a specific tag, there's no need for that, I'm pretty sure you can parse protobuf in place without allocations, which would be a million times faster. You could maybe even do it in Python with reasonable speed.