Add section on input formats

docs/python/code.rst

@@ -134,6 +134,26 @@ Script patterns
 
    - Examples: `extension_registry <https://github.com/open-contracting/extension_registry/blob/master/manage.py>`__, `deploy <https://github.com/open-contracting/deploy/blob/master/manage.py>`__
 
+Input formats
+-------------
+
+JSON
+~~~~
+
+In most cases, simply use the `standard library <https://docs.python.org/3/library/json.html>`__.
+
+For critical paths involving small files, use `orjson <https://pypi.org/project/orjson/>`__.
+
+.. note::
+
+   We can switch to the Python bindings for simdjson, pending `benchmarks <https://github.com/TkTech/pysimdjson/issues/42>`__. For JSON documents with known structures, `JSON Link <https://github.com/beached/daw_json_link>`__ is fastest, but the files relevant to us have unknown structures.
+
+For large files, use the `same techniques <https://ocdskit.readthedocs.io/en/latest/contributing.html#streaming>`__ as OCDS Kit to stream input using `ijson <https://pypi.org/project/ijson/>`__, stream output using `iterencode <https://docs.python.org/3/library/json.html#json.JSONEncoder.iterencode>`__, and postpone evaluation using iterators. See its `brief tutorial <https://ocdskit.readthedocs.io/en/latest/library.html#working-with-streams>`__ on streaming and re-use its `default method <https://ocdskit.readthedocs.io/en/latest/_modules/ocdskit/util.html>`__.
+
+.. note::
+
+   ijson uses `Yajl <http://lloyd.github.io/yajl/>`__. `simdjson <https://simdjson.org>`__ is faster, but is limited to `files smaller than 4 GB <https://github.com/simdjson/simdjson/blob/master/doc/basics.md#newline-delimited-json-ndjson-and-json-lines>`__ and has no `streaming API <https://github.com/simdjson/simdjson/issues/31>`__.
+
 Output formats
 --------------