They wouldn't use amazon.amazon obviously. Some options would include www.amazon, store.amazon, home.amazon, {product_category}.amazon, ec2.amazon, aws.amazon, etc.
See how we're using .google for some examples (which fortunately is a completely made-up word, hence no contentions).
See how we're using .google for some examples (which fortunately is a completely made-up word, hence no contentions).