TypeScript Patterns for Scale

As applications grow, the value of TypeScript's type system becomes increasingly apparent. But beyond basic type annotations lies a rich ecosystem of patterns that enable truly scalable architectures.

The discriminated union pattern is foundational. By using literal types to distinguish between different states, we make impossible states unrepresentable. A network request can be pending, successful, or failed—never multiple simultaneously.

Generic constraints enable powerful abstractions while maintaining type safety. Rather than writing separate functions for arrays, sets, and maps, we can write one properly constrained generic function that works with any iterable.

The builder pattern, when properly typed, provides excellent autocomplete and catches configuration errors at compile time. Each method returns a new builder instance with updated types, making invalid states impossible.

Mapped types and conditional types unlock metaprogramming capabilities. We can derive types from existing types, ensuring consistency across layers. Change your API response type once, and route handlers, validation schemas, and UI components all update automatically.

However, with power comes responsibility. Over-engineering type systems can harm developer productivity. The goal is not the most clever type gymnastics, but the clearest expression of your domain model.

The best TypeScript code reads almost like documentation. Types serve as inline specifications, catching bugs and communicating intent. This is the real value of static typing—not proving theorems, but enabling confident refactoring and fearless iteration.