Exploring the bundle size improvements
Every frontend application needs a number of JavaScript files to run. These files are either the ones you have written yourself or the external dependencies used to build your application, such as MomentJS, Lodash, or RxJS. A bundle is an output of a process that merges all of these files into a few (if not single) files in the most optimized way possible.
One of the major approaches commonly used to improve frontend performance is reducing the JavaScript bundle size. The smaller the size of the JavaScript bundle, the faster a page can load up the first time and be available to users.
The RxJS core team worked on reducing the bundle size of the library in version 7; they did a lot of refactoring to optimize the code and, consequently, the bundle size.
To get a better idea, let's measure the bundle sizes of two frontend applications using RxJS 6 and RxJS 7, respectively, and compare the size of the RxJS library in both applications...