Logs are the operational black box. When something goes wrong, they're nearly the only primary evidence of "what happened." But in distributed systems, logs immediately become a problem. Hundreds of Lambda functions, thousands of containers, on-premises servers all vomiting logs — where do you collect them, how do you order them chronologically, how do you search them, how do you catch specific patterns real-time, and — most practically — how do you control exploding log costs? CloudWatch Logs is the central sink where almost every AWS service streams logs, and on top of it sit real-time routing (Subscription), metric extraction (Metric Filter), and interactive analysis (Insights).