The consolidated feed is a single point of failure

Graduate · enrolled learners

This lesson opens with The Nasdaq SIP flash freeze, 22 August 2013.

What happened

The Securities Information Processor, or SIP, is the system that gathers quotes and trades for Nasdaq-listed stocks from every exchange and publishes them as one consolidated feed, the single authoritative picture of the market that participants rely on. On 22 August 2013 the SIP failed, overwhelmed by a flood of messages from another exchange interacting with a latent software flaw and limited capacity, and because the consolidated feed is the reference everyone depends on to trade fairly, Nasdaq halted trading in all of its listed securities for about three hours. Nothing was hacked and no firm was singled out; a single shared piece of infrastructure that the entire market relied on went down, and when it did, the entire market that relied on it was blind at once. The individual firms' own systems were fine; what failed was the common feed they all trusted, so the failure was not distributed but concentrated in one component whose loss stopped everyone. A dependency shared by the whole market is a risk shared by the whole market.

The decision point

A consolidated data feed that the whole market relies on is a single point of failure for everyone who relies on it, so when it goes down the entire market that depends on it is blinded at the same moment, regardless of how sound each participant's own systems are. The Nasdaq SIP freeze is the case: the one authoritative feed consolidating quotes and trades for Nasdaq-listed stocks failed, and every Nasdaq-listed security was halted for about three hours, not because any firm's own systems broke but because the common feed they all trusted did. This is the concentration version of the course's dark-feed lesson: when a dependency is shared, its failure is not one firm's problem but everyone's at once, and no amount of individual robustness protects a participant from the failure of the infrastructure they all stand on. The insight is that a single point of failure is not only inside your own system; it can be a component the whole market shares, and depending solely on it, however normal and authoritative it is, concentrates your fate in that one component. So the discipline is to recognize where a system depends on a single shared feed or piece of market infrastructure, to understand that such a dependency will take the whole market, including you, down together when it fails, and to plan for that shared failure the way you plan for your own outages, with defined safe behavior rather than an assumption that the authoritative feed cannot fail. The Nasdaq SIP freeze is what a shared single point of failure produces: a whole market blind at once, and the reminder that the feed everyone trusts most is precisely the one whose failure is felt by everyone.

Orientation and Year One are open: anyone can read them without an account. From Year Two onward the lessons are for enrolled learners, because progress through the later years only means anything if it is tracked against a record.

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