What is the canonical way to do clock skew corrections in v4?

[danielmarbach]

It seems there is little guidance available what the canonical way of doing clock skew correction is. One of of dying it seem to be something like

var serviceOperationEndpoint = client.DetermineServiceOperationEndpoint(new ServiceOperationEndpointParameters(new GetCallerIdentityRequest()));
var clockSkew = CorrectClockSkew.GetClockCorrectionForEndpoint(serviceOperationEndpoint.URL);

another way is to use a previous request like

var endpoint = client.DetermineServiceOperationEndpoint(request).URL;
var clockCorrection = CorrectClockSkew.GetClockCorrectionForEndpoint(endpoint);

It seems though that this always call the service and there is no caching underneath. While it seems obvious the URL can be cached, it might still be beneficial to know officially whether that is indeed the case or not. Also, having some updated documentation pointing those things out would be nice because keyword search often returns a very outdated blog post from 2025.

[normj]

I assume in your first example calling DetermineServiceOperationEndpoint you mean config instead of client as the object calling. The service client has the DetermineServiceOperationEndpoint method that takes in the request which forwards to the config version wrapping the request in a ServiceOperationEndpointParameters.

Either version do not make an HTTP request to resolve the endpoint. It runs the request through a generated rules engine to determine the endpoint based on the parameters set on the request and the service client config. For most services there is a single endpoint for a region but there are a handful of services like S3 that use request level parameters to determine the endpoint. Again an HTTP request is never made and I'm not sure a cache mechanism would speed up much here since you would need to do an equality check on the entire request object.

[danielmarbach]

Thanks Norm. Meanwhile I understand it and the context creation and parsing under the covers is quite expensive so I moved it into a place that makes sure we only do it once. Thanks for the r the input

[normj]

Keep in mind the results also depend on the client config including account id that can be obtained from some credential providers. So if you are caching don't cache across different service client instances unless you are going to track any config changes as well.

[danielmarbach]

We cache it per client instance. Going back to some of the comments I made earlier. This is exactly the type of information I think would be helpful to document