Jetpack 4.2.1 dropped today.
We had a rough start last week, but have since been hard at work fixing the performance issues that we had on large networks (8 Million+ users), so be sure to check out the updates for your WordPress site and get the latest version!
While I came in late to the project, having spent the past month or two focusing on SSO for 4.1, it’s been an honor to work with my Poseidon team (Miguel Lezama, Dan Walmsley, Enej Bajgoric) to get this out the door. Many thanks to all Automatticians who also helped make this a possibility by settings up systems, testing, providing feedback, etc.
Jetpack 4.2 and 4.2.1 brings you performance improvements along with some important security updates and enhancements to existing Jetpack modules.
Source: Jetpack 4.2 and 4.2.1: Performance Improvements and More — Jetpack for WordPress