Cloud Watch meritc graph could only query data within 3 hours

You can change the timeline in the center bar above the graphs.

You can read more about CloudWatch metric retention period here: https://aws.amazon.com/about-aws/whats-new/2016/11/cloudwatch-extends-metrics-retention-and-new-user-interface/ And here: https://aws.amazon.com/cloudwatch/faqs/

Perhaps this is the case for you? "Data points with a period of less than 60 seconds are available for 3 hours. These data points are high-resolution custom metrics."