Rule of Three

If same code is used in three distinct locations, hoist it

• If not, then don't abstract away the code and leave them separately

Never leak internals

Example 1: When you are using a vendor "nice messenger" to power your chat system, don't expose that nice messenger is powering your chat system by including it in names

• Instead, name your chat system service instant messenger or social to make it generic so any vendor or system can substitute nice messenger when the underlying implementation needs to change

Example 2: exposing __typename GQL metadata field onto the schema as a data type shape

What is __typename

Source

__typename is a reserved field in GraphQL that returns the name of the object type for a particular GraphQL object

• It is used to determine the type of any object in a GraphQL schema

Every object type in your schema automatically has a field named __typename (you don't need to define it)

__typename is useful is for instance for Apollo client since it uses it for client side cache entries and polymorphism. But should not be used for anything else