Design Patterns Index
Reference notes for Gang-of-Four (GoF) patterns plus common concurrency primitives used in interviews and production systems.
Patterns pair well with LLD case studies and the LLD template.
Creational
How objects are created so construction stays flexible and decoupled from usage.
| Pattern | Guide |
|---|---|
| Singleton | Singleton |
| Factory Method | Factory Method |
| Abstract Factory | Abstract Factory |
| Builder | Builder |
| Prototype | Prototype |
Structural
How classes and objects compose into larger structures.
| Pattern | Guide |
|---|---|
| Adapter | Adapter |
| Bridge | Bridge |
| Composite | Composite |
| Decorator | Decorator |
| Facade | Facade |
| Flyweight | Flyweight |
| Proxy | Proxy |
Behavioral
How objects collaborate and distribute responsibility.
| Pattern | Guide |
|---|---|
| Chain of Responsibility | Chain of Responsibility |
| Command | Command |
| Interpreter | Interpreter |
| Iterator | Iterator |
| Mediator | Mediator |
| Memento | Memento |
| Observer | Observer |
| State | State |
| Strategy | Strategy |
| Template Method | Template Method |
| Visitor | Visitor |
Concurrency
Patterns for parallel work, fan-out/fan-in, async messaging, and failure containment.
| Pattern | Guide |
|---|---|
| Worker pool | Worker pool |
| Fan-out / fan-in | Fan-out / fan-in |
| Pub/sub (concurrency angle) | Pub/sub (concurrency angle) |
| Circuit breaker | Circuit breaker |
Related system-design notes
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