Structured Logging in Node.js: From console.log to Production Observability

Every Node.js service starts with console.log . And for the first thousand requests, it works fine. Then traffic spikes, an incident fires at 3 AM, and you're grepping through gigabytes of unstructured text trying to figure out which user hit which endpoint and why it returned a 500. That's the moment structured logging stops being optional. This article covers the engineering decisions behind production-grade logging: format, transport, correlation, and integration with modern observability stacks. Why console.log Breaks at Scale console.log has three fundamental problems in production: No structure. Output is a flat string. You can't filter, query, or aggregate without regex hacks. No levels. Everything is the same priority. When your service emits 10,000 lines per minute, you need to distinguish a fatal database disconnection from a debug cache miss. Synchronous stdout. In Node.js, console.log writes to stdout synchronously. Under heavy load, this blocks the event loop. Measured lat