How to generate AWS CloudWatch Alarm which involves multiple Metrics

Question

Need to generate CloudWatch Alarm for API Gateway and Lambda functions.

For API Gateway CloudWatch Alarm should be generated if 5XX Error count is 10% of total request count at given period (eg 5 minutes).

Similarly, We need to add a metric if Maximum Latency 6% of total request count > 4 seconds.

For such type of metric looks like we need a combination of metric like Sum of total requests and than need to calculate percentage of errors.

We have Math Expressions/Metric math which might be used. Is there any other way to achieve this?

Any help is appreciated!

Answer 1

EDIT: Its now possible to create alarms on Metric expressions from the CloudWatch Console.

Original Answer below:

Unfortunately its not possible to create alarms based on Metric expressions in CloudWatch. Your best bet may be the M of N thresholds in alarms, for example: If num_of_errors > 5 for 3 datapoints in 5 minutes. Its not exactly what your asking for, but may be a good start. Best of luck!