• Since joining the Core Team I have focused on improving Rails to work well with applications as they grow by focusing on database scalability and performance. In Rails 6 and 7, I implemented support for multiple databases and database sharding (referenced in this book in the Multiple Databases Section).
• The Rails framework is unique because it has matured alongside the companies that use it. We’re not exaggerating when we say that Rails can take you from “Hello, World!” to IPO; so many applications that were started on Rails 1.0 are not just running today, but thriving. This evolution and symbiotic relationship between Rails and the companies that use it come from the belief the community has in contributing to open source. The companies that depend heavily on Rails success know they have a direct role in that success. Without contributors there would be no Rails and I’m incredibly proud of the community we’ve built.
• Remember that technical books are the beginning of your learning adventure, not the end.
• While Rails 5, 6, and 7 do not bring a giant leap forward in features as their predecessors did, it gives us a level of fit and finish that surpasses any major technology framework that we have worked with. Everything. Just. Works.
• Rails 6 marked the beginning of a revolution, though: After years of using their own, forked version of an older revision of Rails, GitHub came back to the same Ruby on Rails we all use and love. This bears first fruit with contributions from their database and test setup in Rails 6. With GitHub, Shopify, and of course Basecamp and Hey all running the latest version of Rails, your app will be in good company. Rails 7 continues with At-Work encryption extracted from Basecamp and async loading from Shopify.
• Whenever you write code that feels like plumbing, by which we mean entirely unrelated to the business domain of your application, you’re probably doing too much work.
• Ruby on Rails is a vast ecosystem of core code, official plugins, and third-party plugins. That ecosystem has been exploding rapidly and provides all the raw technology you need to build even the most complicated enterprise-class web applications.
• Rails is foremost a web framework and, at least to us, the controller and routing implementation is the most unique, powerful, and effective feature, with Active Record following a close second.

[Rails] gained a lot of its focus and appeal because I didn’t try to please people who didn’t share my problems. Differentiating between production and development was a very real problem for me, so I solved it the best way I knew how. — David Heinemeier Hansson

• Rails applications have always been preconfigured with three standard modes of operation: devel- opment, test, and production. These modes are execution environments and have a collection of associated settings that determine things such as which database to connect to and whether the classes of your application should be reloaded with each request. It is simple to create your own custom environments if necessary.
• Bundler6 is not a technology specific to Rails, but it is the way to manage your application’s Rubygem dependencies. Applications generated with Rails use Bundler automatically, and bundler is a dependency of Rails itself. One of the most important things that Bundler does is dependency resolution on the full list of gems specified in your configuration, all at once.
• Running commands prefixed with bundle exec ensures that your code can require all the correct gem versions and none of the incorrect ones. It does that by adjusting the Ruby load path. Furthermore, it guarantees that the right executable path for those gems is available in the shell’s search path.
• As people tend to forget to prefix the command with bundle exec, Bundler offers the concept of binstubs. They are small shell scripts that load up Bundler first to ensure that you are loading the correct executable.
• To add a binstub of a commonly used executable in your bundle, invoke bundle binstubs some-gem-name. Note that you need to provide the name of the gem (which will generate binstubs for all its executables).