With respect to cloud billing management systems, what is the difference between pre-usage and post-usage billing?

What is public key infrastructure and explain-how can it used within a cloud computing environment?

When considering a migration from an existing, internal data center to a cloud environment, describe examples of upfront and ongoing costs that would needs to be considered when analyzing the cost of such an effort?

What are locked-in costs and what considerations should be made with respect to locked-in costs when considering a migration to cloud computing?

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