@Override
    public URI getServiceEndpoint() {
        String serviceEndpoint = region.getServiceEndpoint(serviceName);

        if (serviceEndpoint == null) {

            serviceEndpoint = String.format("%s.%s.%s", serviceName, region.getName(), region.getDomain());

            log.info("{" + serviceName + ", " + region.getName() + "} was not "
                    + "found in region metadata, trying to construct an "
                    + "endpoint using the standard pattern for this region: '" + serviceEndpoint + "'.");

        }
        return toURI(stripProtocol(serviceEndpoint));
    }
Uses region metdata to construct an endpoint for a specific service
aws-java-sdk-core/src/main/java/com/amazonaws/internal/DefaultServiceEndpointBuilder.java