Introduction to API Design Patterns

What are API Design Patterns?

A software design pattern is a particular design that can be applied over and over to lots of similar software problems, with only minor adjustments. It is not a pre-built library but more of a blueprint for solving similarly structured problems.

• Most often, design patterns focus on specific components rather than entire systems.
  • e.g. If you want to add a logging system, you can use the singleton design pattern.
  • This pattern is not complete
  • However, it's well-defined and well-tested pattern to follow when you need to solve this small compartmentalised problem of always having a single instance of a class.

Why are API Design Patterns Important?

• While having programmatic access to a system is very valuable, it's also much more fragile and brittle.
  • Changes to the interface can easily cause failures for those using the interface.
• We refer to this aspect as flexibility
  • Interfaces where users can easily accommodate changes are flexible
    • GUIs are flexible - moving a button
  • Interfaces where even small changes cause complete failures are rigid.
    • Backend APIs: changing a query parameter breaks old client code.
• Rigid interfaces make it much more difficult to iterate toward a great design.
  • We are often stuck with all design decisions, both good and bad.

Pagination Pattern: The pagination pattern is a way of retrieving a long list of items in smaller, more manageable chunks. The pattern relies on extra fields on both the request and response.

Moving from a non-paginated to paginated response pattern:

Q. What happens if we don't start with the pattern?

1. All previously written clients are expected all the data in one list - it has no way of getting subsequent pages.
2. Clients are left to think they have all the data - which can lead to incorrect conclusions.