alt Hacker News> The real cost with JSON is when you have a 200MB manifest or build artifact and you need exactly two fields out of it.
There are SAX-like JSON libraries out there, and several of them work with a preallocated buffer or similar streaming interface, so you could stream the file and pick out the two fields as they come along.
You still have to parse half the entire file on average. Much slower than formats that support skipping to the relevant information directly.