I’ve recently encountered an issue where AWS OpenSearch becomes unreliable during a specific time window on the 1st day of each month.
The problem occurs between 8 AM and 1 PM (UTC+8). During this time, signature verification fails, but everything works fine outside of this window.

The issue is peculiar because:

1. Direct connections to Elasticsearch are unaffected.
2. Directly querying Elasticsearch is not an issue.
3. Different versions of OpenSearch using the same key still experience the issue.
4. Requests made through my Go and Ruby on Rails projects exhibit intermittent issues. Out of five attempts, approximately three or four will succeed, while the others fail with the following error message:

{
    "message": "The request signature we calculated does not match the signature you provided. Check your AWS Secret Access Key and signing method. Consult the service documentation for details.nnThe Canonical String for this request should have beenn'GETn/users/...."
}

I’m unsure if this could be related to timezone settings or if something else is missing in the configuration. Both the Go and Ruby on Rails projects use the AWS SDK provided by AWS.

Any insights or suggestions on how to resolve this issue would be greatly appreciated.