How to use a DHT for a social trading environment

Question

I'm trying to understand if a DHT can be used to solve a problem I'm working on:

I have a trading environment where professional option traders can get an increase in their risk limit by requesting that fellow traders lend them some of their risk limit. The lending trader can either search for traders with certain risk parameters which are part of every trader's profile, i.e. Greeks, or the lending trader can subscribe to requests from certain traders who are looking for risk.

I want this environment to be scalable and decentralized, but I don't know how traders can search for specific profile parameters when the data is contained in a DHT. Could anybody explain how this can be done?

Update:
An example that might make it easier to understand might be SO, but instead of running as a web application, the Risk Exchange runs as a desktop application on each trader's workstation. The request for risk are like questions (which may be tagged by contract, exchange, etc) and each user has a profile which shows their history of requests, their return on borrowed risk, etc.

Obviously the "exchange" can be run on a server, but I was hoping to decentralize it and make it scalable so that the system may support an arbitrary number of traders. How can I search for keywords, tags, and other data pertaining to a trader's profile if this information is stored in a distributed hash table?

Answer 1

Your question holds a contradiction in my ears. DHT is a great way of distributing data in a decentralized manner, but cannot provide the nodes with an information overview. This means that any overview action, such as questioning the network for certain data, will have to be done at a centralized collection point. Solutions to this contradiction has been created, but their fault tolerance does not match a critical system such as financial trading.

So my answer would be to use a centralized server to hold an overview cache of the DHT network.