The second part of our series was about caching headers - and in the pro tip about strong vs. weak ETags we briefly teased that strong ETags have a second job: They protect you from lost updates when writing. That’s exactly what today is about.

In the first part of our series, we looked at QUERY, the first new HTTP method in 15 years. Today we’re talking about something you probably use every day without really understanding what you’re doing with it: caching headers.

In the first part of this series, we looked at Google Truth from the ground up - why it exists, how the subject model works, and when assertions become readable instead of cryptic.