Simon Willison’s Weblog

We Rewrote JSONata with AI in a Day, Saved $500K/Year. Bit of a hyperbolic framing but this looks like another case study of vibe porting, this time spinning up a new custom Go implementation of the JSONata JSON expression language - similar in focus to jq, and heavily associated with the Node-RED platform.

As with other vibe-porting projects the key enabling factor was JSONata's existing test suite, which helped build the first working Go version in 7 hours and $400 of token spend.

The Reco team then used a shadow deployment for a week to run the new and old versions in parallel to confirm the new implementation exactly matched the behavior of the old one.