The web’s caching model served us well for over two decades. Recently, in the name of privacy, it’s undergone a fundamental shift that challenges many of our performance optimization assumptions. This is called Double-keyed Caching or cache-partitioning more generally. Here’s what changed, why it matters, and how to adapt. How Caching Used to Work (Pre-2020) In the traditional model, browsers maintained a simple key-value store for cached resources: cache = { "https://cdn.example.com/jquery-3.6....