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AWS CloudWatch Logs provides a scalable, reliable way to collect and monitor log data from your applications and infrastructure. Two foundational concepts in this service are log streams and log groups. In this guide, we’ll break down each concept, compare them side by side, and show how they fit into an effective AWS logging strategy.

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What Is a Log Stream?

A log stream is an ordered sequence of log events that all originate from the same source—for example, an EC2 instance, Lambda function, or on-premises server. Each event carries a timestamp and a message, forming a timeline of activity for that component. Common log stream contents include:
  • Application error messages
  • User access and transaction logs
  • Performance and diagnostics data
Each log stream is unique to its source. You can have multiple streams for different instances of the same application.

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What Is a Log Group?

A log group acts as a container for one or more log streams. Think of it as a logical folder that centralizes related streams under common settings and policies. Within a log group, you can configure:
  • Retention period: How long to keep log data
  • Metric filters: Generate CloudWatch metrics from log patterns
  • Access control: IAM policies governing who can view or manage logs
The image explains the concepts of AWS CloudWatch Log Stream and Log Group, showing that a Log Group contains multiple Log Streams.
Setting a very long retention period can increase storage costs. Review your compliance requirements before adjusting retention.

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Log Stream vs. Log Group: At a Glance

ConceptDefinitionKey Use Cases
Log StreamTimestamped sequence of events from a single sourceTroubleshooting individual instances or components
Log GroupContainer for multiple streams with shared settingsCentralized management, retention, and monitoring

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Next Steps

In upcoming lessons, we’ll explore how to:
  • Define and parse log events in CloudWatch Logs
  • Create metric filters to extract actionable insights
  • Integrate AWS CloudWatch Logs with CloudWatch Alarms

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References

Use these resources to deepen your understanding and streamline your AWS logging architecture.

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