# Patterns
All Patterns notes →01 — Layering Patterns
Layered Architecture, Hexagonal (Ports & Adapters), Onion, Clean Architecture, and Screaming Architecture — how each draws the boundary between domain logic and infrastructure, and what that boundary costs.
02 — Domain Modeling Patterns
DDD's tactical toolkit: Rich Domain Model vs. Anemic Model, Aggregate, Entity, Value Object, Repository, Factory, and Specification — the vocabulary a domain model needs to stay consistent under concurrent writes.
03 — Transaction Patterns
Unit of Work, Identity Map, Lazy Loading, and Optimistic vs. Pessimistic Locking — the patterns that keep an object graph and its persisted state from drifting apart.
04 — Integration Patterns
DTO, Gateway, Data Mapper, Service Layer, Table Data Gateway, and Active Record — the patterns that mediate between a domain model and everything outside it (databases, external services, the wire).