Project Size
Like a lot of decisions in programming, deciding to make a new Nx project or not is all about trade-offs. Each organization will decide on their own conventions, but here are some trade-offs to bear in mind as you have the conversation.
What is a Project For?
Developers new to Nx can be initially hesitant to move their logic into separate projects, because they assume it implies that those projects need to be general purpose and shareable across applications.
This is a common misconception, moving code into projects can be done from a pure code organization perspective.
Ease of re-use might emerge as a positive side effect of refactoring code into projects by applying an "API thinking" approach. It is not the main driver though.
In fact when organizing projects you should think about your business domains.
Should I Make a New Project?
There are three main benefits to breaking your code up into more projects.
1. Faster Commands
The more granular your projects are, the more effective nx affected and Nx's computation cache will be. For example, if projectA contains 10 tests, but only 5 of them were affected by a particular code change, all 10 tests will be run by nx affected -t test. If you can predict which 5 tests are usually run together, you can split all the related code into a separate project to allow the two groups of 5 tests to be executed independently.
2. Visualizing Architecture
The nx graph command generates a graph of how apps and projects depend on each other. If most of your code lives in a few giant projects, this visualization doesn't provide much value. Adding the --watch flag to the command will update the visualization in-browser as you make changes.
3. Enforcing Constraints
You can enforce constraints on how different types of projects depend on each other using tags. Following pre-determined conventions on what kind of code can go in different types of projects allows your tagging system to enforce good architectural patterns.
Also, each project defines its own API, which allows for encapsulating logic that other parts of codebase can not access. You can even use a CODEOWNERS file to assign ownership of a certain project to a user or team.
Should I Add to an Existing Project?
Limiting the number of projects by keeping code in an existing project also has benefits.
1. Consolidating Code
Related code should be close together. If a developer can accomplish a task without moving between multiple different folders, it helps them work faster and make less mistakes. Every new project adds some folders and configuration files that are not directly contributing to business value. Nx helps reduce the cost of adding a new project, but it isn't zero.
2. Removing Constraints
Especially for rapidly evolving code, the standard architectural constraints may just get in the way of experimentation and exploration. It may be worthwhile to develop for a while in a single project in order to allow a real architecture to emerge and then refactoring into multiple projects once the pace of change has slowed down.