One of the REAL bottlenecks in a large SELL-side FX dealer system is tiered pricer. Trigger event could be a market data change. Since such an event could trigger an avalanche of messages, the frequency of such events is not very high, probably below 10 events/second on 1 currency pair. If you have 10(or 50 or whatever) active currency pairs, then you could get 100 triggers/sec through your entire system.
Once a trigger is activated, pricer computers new bid/ask quotes for Tier 1 Gold clients. Pricer then adds a distinct spread for each tier. For an active pair like EUR/USD, there can be 1900 tiers. There can be up to 1900 (non-unique) pairs of bid/ask quotes. Typically, the “best” quotes would have a bid/ask spread of 2 to 3 pip, applicable to the best and largest clients. For a *retail* client, it could be 20 – 40 pips.
Core of the tiered pricer is a Drools rule engine.
Another module is the messaging engine using Nirvana by My-Channels. If a particular bid/ask quote applies for all (say, 20) tiers in Silver category, then pricer broadcast the quote to a topic like Quote.EURUSD.Silver. This is kind of alias for 20 different “tier” topics. For efficiency, this is probably multicast.
In the worst case, one event can trigger an avalanche of 1900 messages for one currency pair alone.
Last module is the FIX engine. Quotes often go out the door in FIX format, just as RFQ. Now there are 1900 tiers but the number of clients could be higher or lower than 1900. If there are more than 1900 clients and if all of them subscribe to our quote, then each must be sent the quote. I know a Chicago prop trading firm (Gelber?) subscribe to a lot of “bank feeds”.
The most demanding type of subscription is a RequestForStream (RFS). A typical RFS could ask for a stream of EURUSD quotes for 10 (up to 120 minutes), during which time all quotes must be delivered.
Unlike RFQ, RFS requires special approval. The bid/ask quotes in an RFS can be indicative or *executable* (similar to Firm, but see separate blot post). If a client hit an executable bid or lift an executable offer, then the trade is considered executed, though I believe cancellation is still a possibility, just like any Firm quote in bonds.
How does a dealer make sure he has enough position to honor the quote? Perhaps by setting aside reserve quantities, or by monitoring the open market.
Unlike bidwanted systems, a quote is not non-negotiable. It’s possible for a client to negotiate electronically, though I feel manual negotiation is more practical.