Designing a Scalable Logger System in Java: A Low-Level Design Guide

This article presents a low-level design for a Java logger framework supporting multiple log levels (DEBUG to FATAL) and output destinations (console, file, database, with future Kafka/ElasticSearch). It uses design patterns like Singleton, Strategy, and Factory to ensure thread safety, extensibility, and loose coupling. The guide includes code examples for LogLevel enum, LogMessage class, and appender interfaces.