Based on the information provided, it seems that you are experiencing performance degradation with the response time of the `respondDecisionTaskCompleted` call in your workflow application using the JavaScript AWS SDK. Here are some suggestions on what you can look into to troubleshoot and address the issue:

1. **Resource Leaks**: Since you mentioned that the response time becomes faster after redeploying the application, there might be a resource leak in your application causing performance degradation over time. Check for any resource leaks such as open connections, unclosed resources, or memory leaks that could be accumulating and impacting the response time.

2. **AWS SDK Configuration**: Ensure that your AWS SDK configuration is optimal for performance. You can review the configuration settings related to retries, timeouts, and connection management to see if any adjustments can be made to improve the response time.

3. **AWS SWF Service Limits**: Check if you are hitting any service limits or throttling issues with AWS SWF that could be causing delays in the response time. Monitor your AWS service quotas and metrics to ensure you are within the limits.

4. **Network Latency**: Evaluate the network latency between your application and the AWS SWF service. High network latency could contribute to slower response times. Consider running network diagnostics or tests to identify any potential network issues.

5. **Code Optimization**: Review your code implementation for the `respondDecisionTaskCompleted` call and ensure it is optimized for performance. Avoid any unnecessary processing, repeated calls, or inefficient code that could impact the response time.

6. **Logging and Monitoring**: Implement logging and monitoring in your application to track the performance metrics, identify bottlenecks, and analyze the behavior of the `respondDecisionTaskCompleted` calls. Use tools like CloudWatch to capture and analyze performance data for insights.

By investigating these areas and making necessary optimizations, you can troubleshoot the slow response time issue in your workflow application using the JavaScript AWS SDK.