Logging Best Practices with SLF4J and Logback

Logging is often an afterthought until something goes wrong. I’ve been on calls where we were trying to debug a failure and realized the logs were either too verbose or had no context. Using SLF4J with Logback is the standard in the Java world. The most important advice I can give is to use parameterized logging: `log.debug("User {} logged in at {}", user, time)`. Never use string concatenation. Why? Because if the log level is set to INFO, the string concatenation still happens, wasting CPU cycles. Also, structure your logs. Don’t just log plain text; use JSON format if you’re in a containerized environment. Tools like ELK or Datadog can parse JSON logs to give you dashboards. And please, include the request ID in your logs. When you’re debugging a request that passes through 5 microservices, a correlation ID makes it possible to trace the entire flow.