Hexagonal architecture, also known as ports and adapters, is a design pattern that isolates core business logic from external concerns like databases, UIs, and APIs. This post walks through a common scenario: a system initially built with MySQL that later needs to support MongoDB or a new CLI interface. Without hexagonal architecture, such changes require rewriting business logic scattered across infrastructure code. The pattern introduces ports (interfaces) and adapters (implementations) so that the core remains untouched. For overseas engineering leaders, this is a mature concept but one that still trips up teams during refactoring. The value lies not in novelty but in the clear, example-driven explanation of trade-offs. Teams evaluating microservices or modular monoliths will find this a useful reference for maintaining long-term system flexibility.
A practical look at hexagonal architecture for solving real-world migration and multi-interface challenges.