Agreed on jsons not being ordered.

The docs on simdjson mention that if you parse the fields in the order as they appear on file, then simdjson can do it in one iteration. If you get fields in random order, simdjson will have to loop the data a few times.

If your json on disk is

  { "field1": "val1", "field2": "val2" }

then it is faster to say (pseudo C++)

  simdjson::document_reference elem;
  std::string_view tmp;
 
  elem["field1"].get_string().get(tmp);
  elem["field2"]...

than the other way around. This works only if you know what you are looking for and it is consistent on disk. Note that you are reading from an iterator that consumes the value: getting a field twice gives an error; totally different than reading from a dict.

See also [1] under "Extracting Values: You can cast a JSON element to a native type..."

[1] https://github.com/simdjson/simdjson/blob/master/doc/basics....

Ah yes, that makes sense. Thanks a lot for explaining!