"In a year since Facebook’s blog about Cache-Control Immutable, we can see that it’s usage has spread beyond Facebook and is being used by a handful of large 3rd parties and ~4150 additional domains. Across all of the pages in the HTTP Archive, 2% of requests and 30% of sites appear to include at least 1 immutable response. Additionally, most of the sites that are using it have the directive set on assets that have a long freshness lifetime."

"Functional programming contains many ideas that we can use to make our own code simpler and better. Pure functions and immutable data minimise the hazards of side effects. Declarative programming maximises code readability. These are important tools that should be embraced in the fight against complexity."

"Databases are global, shared, mutable state. That’s the way it has been since the 1960s, and no amount of NoSQL has changed that. However, most self-respecting developers have got rid of mutable global variables in their code long ago. So why do we tolerate databases as they are?"

Immutable persistent data collections for Javascript which increase efficiency and simplicity.