I'm convinced that GitHub's decision to move away from Rails was partly influenced by a significant flaw in ActiveRecord: its lack of support for composite primary keys. The need for something as basic as PRIMARY KEY(repo_id, issue_id) becomes unnecessarily complex within ActiveRecord, forcing developers to use workarounds that involve a unique key alongside a singular primary key column to meet ActiveRecord's requirements—a less than ideal solution.
Moreover, the use of UUIDs as primary keys, while seemingly a workaround, introduces its own set of problems. Despite adopting UUIDs, the necessity for a unique constraint on the (repo_id, issue_id) pair persists to ensure data integrity, but this significantly increases the database size, leading to substantial overhead. This is a major trade-off with potential repercussions on your application's performance and scalability.
This brings us to a broader architectural concern with Ruby on Rails. Despite its appeal for rapid development cycles, Rails' application-level enforcement of the Model-View-Controller (MVC) pattern, where there is a singular model layer, a singular controller layer, and a singular view layer, is fundamentally flawed. This monolithic approach to MVC will inevitably lead to scalability and maintainability issues as the application grows. The MVC pattern would be more effectively applied within modular or component-based architectures, allowing for better separation of concerns and flexibility. The inherent limitations of Rails, especially in terms of its rigid MVC architecture and database management constraints, are significant barriers for any project beyond the simplest MVPs, and these are critical factors to consider before choosing Rails for more complex applications.
Do you have any sources on GitHub moving away from Rails? This is the first that I've heard and my googlefu has returned zero results around this. Just last year they had a blog post around Building GitHub with Ruby and Rails[0] so your remark caught my off guard.
Perhaps too late, but Rails 7.1[1] introduced composite primary key support, and there's been a third-party gem[2] offering the functionality for earlier versions of ActiveRecord.
Whilst I would agree that a monolith can run into scalability issues, I am not sure your characterisation of Rails as such is proportionate.
To say that Rails' architecture is a "sigificant barrier for any project beyond the simplest MVPs" is rather hyperbolic, and the list of companies running monolithic Rails apps is a testament to that.
On this very topic, I would recommend reading GitLab's own post from 2022 on why they are sticking with a Rails monolith[1].
I can't really comment on GitHub, but Rails supports composite primary keys as of Rails 7.1, the latest released version [1].
About modularity, there are projects like Mongoid which can completely replace ActiveRecord. And there are plugins for the view layer, like "jbuilder" and "haml", and we can bypass the view layer completely by generating/sending data inside controller actions. But fair, I don't know if we can completely replace the view and controller layers.
I know I'm missing your larger point about architecture! I don't have so much to say, but I agree I've definitely worked on some hard-to-maintain systems. I wonder if that's an inevitability of Rails or an inevitability of software systems—though I'm sure there are exceptional codebases out there somewhere!
Moreover, the use of UUIDs as primary keys, while seemingly a workaround, introduces its own set of problems. Despite adopting UUIDs, the necessity for a unique constraint on the (repo_id, issue_id) pair persists to ensure data integrity, but this significantly increases the database size, leading to substantial overhead. This is a major trade-off with potential repercussions on your application's performance and scalability.
This brings us to a broader architectural concern with Ruby on Rails. Despite its appeal for rapid development cycles, Rails' application-level enforcement of the Model-View-Controller (MVC) pattern, where there is a singular model layer, a singular controller layer, and a singular view layer, is fundamentally flawed. This monolithic approach to MVC will inevitably lead to scalability and maintainability issues as the application grows. The MVC pattern would be more effectively applied within modular or component-based architectures, allowing for better separation of concerns and flexibility. The inherent limitations of Rails, especially in terms of its rigid MVC architecture and database management constraints, are significant barriers for any project beyond the simplest MVPs, and these are critical factors to consider before choosing Rails for more complex applications.