Sorry, I need to add a small correction for my previous email: JsonParser::getKeyValue() wouldn't allow parsing a truncated JSON document. The on-demand parsing API I mentioned in my opening message is what would make such use-case possible.
Besides, I accept if you feel it's too early for a new JSON API to be added to the core, so if the majority of stakeholders also share this opinion, I'll try to make an improved version of ext/simdjson available via PECL. Máté
