pinojs/pino

Pino is a logging library for Node.js, the server-side JavaScript runtime, designed to record what your application is doing while keeping the performance cost as low as possible. Logging means writing out messages at runtime (like "user logged in" or "database query failed") so you can monitor, debug, or audit your application. The key problem Pino addresses is that logging, if done carelessly, can slow down a server under load. Every log write takes CPU time, and when logs pile up in a busy app they can reduce how many requests per second your server can handle. Pino tackles this by keeping its own processing overhead very small, according to the README it is over 5x faster than comparable alternatives, and by recommending that any expensive operations like sending logs to external services or reformatting them happen in a separate worker thread (called a "transport") rather than in your main application thread. Pino writes logs as JSON, which makes them easy to parse and search with other tools. The basic usage is a few lines: require the library, call logger.info() or similar methods, and each log entry is written as a JSON object with the level, timestamp, message, and any extra properties you attach. You can also create "child" loggers that inherit a set of properties, useful for tagging all log lines from a particular request or user session. It installs via npm, integrates with common Node.js web frameworks, and works in browser environments with a separate browser-compatible API. You would use it when building a Node.js server and want structured, fast, JSON-formatted application logs.