Type Design for Performance

When to Use This Skill

Use this skill when:

• Designing new types and APIs
• Reviewing code for performance issues
• Choosing between class, struct, and record
• Working with collections and enumerables

Core Principles

1. Seal your types - Unless explicitly designed for inheritance
2. Prefer readonly structs - For small, immutable value types
3. Prefer static pure functions - Better performance and testability
4. Defer enumeration - Don't materialize until you need to
5. Return immutable collections - From API boundaries