Add store API experiment

@barakmich For example, you have keys at horizon 10000.
/foo/1
/foo/2
/foo/3
...
/foo/10000

The first request would be list(10000, /foo, 0, /foo/1, /foo/1000)
then second one would be list(10000, /foo, 0, /foo/1000, /foo/2000)