Practical Limit on number of Azure Shared Access Signatures?

I'm looking to avoid having to use a handler/module in my Webrole to protect images being served up from Block Blob storage on Azure. Shared Access Signatures (SAS) seems to be the way to go.

My question, is there a practical limit on the number of SAS I can issue - Could I issue one every 1 minute, say? Is there a performance issue (time to issue SAS) that would be the limiting factor?

I had initially thought that one SAS per user session would protect me better than a single SAS, but since there is nothing tying a SA开发者_运维技巧S to a user, that won't help...

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Shared Access Signatures have an optional component called a "container-level access policy." If you used a container-level access policy, that actually gets stored in blob storage and has a limit of five per container.

If you don't use a container-level access policy, you can make as many Shared Access Signatures as you want, and the server isn't even involved. (The signature is generated locally, meaning in your web role instance.) Generated the signature does involve some crypto, so you may eventually peg the CPU, but I suspect it's "fast enough."