ask for advice for data access design pattern

Question

Hello everyone,

I am designing a library which client side could use it to retrieve content from a remote cache server, through Http/Web Services communication.

My current issues and concerns are,

- I want to let client side library to start multiple threads to work efficiently to request for multiple content at the same time other than a single thread pattern;
- But I do not want to hit the server too hard and I also do not want to the library to consume too much resources (memory/threads) on client side to block other work of the client. The library is delivered as a DLL, so loaded into client side process, and will compete for resources of the same process.

Are there any good design patterns for such issues?

thanks in advance,
George