# Content Domain 4: Troubleshooting and Optimization
<a name="developer-associate-03-domain4"></a>

**Topics**
+ [Task 4.1: Assist in a root cause analysis.](#dva-03-task4.1)
+ [Task 4.2: Apply logging, monitoring, and observability best practices.](#dva-03-task4.2)
+ [Task 4.3: Optimize applications by using AWS services and features.](#dva-03-task4.3)

## Task 4.1: Assist in a root cause analysis.
<a name="dva-03-task4.1"></a>
+ Skill 4.1.1: Debug application code and service integration issues to identify defects.
+ Skill 4.1.2: Interpret application metrics, logs, and traces.
+ Skill 4.1.3: Query logs to find relevant data.
+ Skill 4.1.4: Troubleshoot deployment failures by using output logs.
+ Skill 4.1.5: Use AWS AI tools to analyze errors and to generate troubleshooting suggestions.

## Task 4.2: Apply logging, monitoring, and observability best practices.
<a name="dva-03-task4.2"></a>
+ Skill 4.2.1: Implement effective logging strategies to record application behavior and state (for example, by using structured logging for application events and user actions).
+ Skill 4.2.2: Implement code that emits custom metrics.
+ Skill 4.2.3: Implement notification alerts for specific actions (for example, quota limits, deployment completions).
+ Skill 4.2.4: Implement tracing by using AWS services and tools.
+ Skill 4.2.5: Monitor workload health (for example, by using application health checks, liveness and readiness probes).

## Task 4.3: Optimize applications by using AWS services and features.
<a name="dva-03-task4.3"></a>
+ Skill 4.3.1: Apply concurrency concepts (for example, AWS Lambda provisioned concurrency, Amazon EC2 Auto Scaling, thread pool management, connection pooling).
+ Skill 4.3.2: Optimize memory and compute power for an application.
+ Skill 4.3.3: Optimize application messaging (for example, by using Amazon SQS queues, Amazon SNS fan-out patterns).
+ Skill 4.3.4: Implement caching by using AWS services (for example, Amazon ElastiCache, Amazon DynamoDB Accelerator [DAX], Amazon CloudFront).
+ Skill 4.3.5: Detect performance bottlenecks by using AWS services (for example, Amazon CloudWatch).
+ Skill 4.3.6: Use AWS AI tools to identify optimization opportunities (for example, performance bottleneck detection, resource usage optimization, code efficiency improvement).