It depends on your requirements for performance.
We have UI virtualization implemented in place. We also have data engine for sorting, grouping and filtering which is very fast and is done for the WP7 especially. We can say that RadJumpList is definitely optimized for performance.
That said - you should test and see if it matches your requirements. Our advice is if you can - load as little data as possible, because all this is executed in phone environment where you have limitations for CPU and memory usage.
Are these 20k records saved on the phone? Can you load them in batches? If you give us more details on your scenario - we can give you some insights. You can read my series
of blog posts
on RadJumpList - this one for optimizing performance specifically
Please let us know how it goes.
All the best,
the Telerik team
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