As mentioned by Ed Anuff in his blog and slides, one way to build customized secondary index is:
We use one CF, each row to represent a secondary index, with the secondary index name as row key.
For example,

Indexes = {
"User_Keys_By_Last_Name" : {
"adams" : "e5d61f2b-",
"alden" : "e80a17ba-",
"anderson" : "e5d61f2b-",
"davis" : "e719962b-",
"doe" : "e78ece0f-",
"franks" : "e66afd40-",
: ,

But the whole secondary index is partitioned into a single node, because of the row key.
All the queries against this secondary index will go to this node. Of course, there are some replica nodes.

Do you think this is a scalability problem, or any better solution to solve it?