By Alexander Osipovich and Kimberley Kao
Inside a nondescript, boxy building in a Chicago suburb, the heat was rising. This wasn't just an unusual issue for a chilly fall day in Illinois. It was also a problem for global markets.
The facility was a vital data center used by CME Group, the exchange operator behind some of the most heavily traded instruments in international finance -- futures tied to U.S. stock indexes, Treasurys, crude oil and more. And temperatures inside the building were soaring toward 120 degrees Fahrenheit.
The result was an outage lasting more than 10 hours, slamming the door on trading in these key contracts from late on Thanksgiving evening through to an hour before Wall Street trading opened on Friday morning. While it didn't stop buying and selling of underlying bonds and stocks, it limited investors' room to maneuver and made it harder to gauge how U.S. markets would move in the final session of the month.
In some ways, it was a lucky break, coming during a slow holiday period in the U.S., and mostly resolving before American markets opened. It was also another warning about vulnerabilities in the digital economy: There were echoes of the recent outages at Amazon Web Services and Cloudflare that took down swaths of the internet. The disruptions show what can go wrong when a widely used service that businesses and consumers expect to function around the clock, hits even an apparently mundane technical problem.
Futures aren't like stocks, where trading is spread across a number of exchanges, such as the New York Stock Exchange or Nasdaq Stock Market. The U.S. futures market is highly concentrated at CME. The company, which owns the Chicago Mercantile Exchange and other trading venues, handles the lion's share of volume in key areas such as interest-rate and stock-index contracts.
If NYSE's New Jersey data center goes down, "all the other people just keep on trading," said James Angel, a finance professor at Georgetown University. But on the futures side, "the concentration in CME becomes a single point of failure."
The exchange blamed the outage on a cooling issue at the main electronic-trading hub for CME's markets in Aurora, Ill., a western suburb of Chicago.
Temperatures in the facility rose to around 120 degrees Fahrenheit in the hours after the air conditioning failed, people familiar with the matter said. Data centers, which consist of vast arrays of servers crunching information, must be constantly cooled to prevent overheating.
The Aurora data center is run by another company, CyrusOne, which bought it from CME in 2016. CyrusOne apologized for the disruption, which it said stemmed from "a chiller plant failure affecting multiple cooling units."
The company said it dispatched engineers to address the overnight emergency, bringing in temporary cooling equipment as they raced to fix the main cooling system.
Privately held CyrusOne operates dozens of data centers worldwide. It has been owned by the investment firms KKR and Global Infrastructure Partners since 2022. In recent years, the company has also sought to meet the needs of the artificial-intelligence boom, which has led to a massive build-out of energy-hungry data centers across the country.
The outage -- which also disrupted bond and currency-trading platforms that CME operates -- underscored how much markets depend on the smooth functioning of the Aurora data center. It was felt as far afield as Kuala Lumpur, where Malaysia's exchange operator halted trading on its derivatives market.
In the warehouselike site near Interstate 88, CME's core trading systems sit alongside the servers of high-frequency trading firms eager for near-instant data access. The facility is surrounded by antennas, which these trading outfits use to rapidly relay price moves to other financial hubs worldwide.
It wasn't immediately clear why CME didn't switch to using its backup data center in the New York area. One potential issue is that large trading firms that quote prices on CME don't have robust technical infrastructure at the backup site, and would prefer to simply wait out an outage at Aurora, some of the people familiar with the matter said.
As well as the Chicago Mercantile Exchange, CME owns former rivals such as the crosstown Chicago Board of Trade, the New York Mercantile Exchange, and the Commodity Exchange, also known as Comex.
The derivatives that CME handles are crucial to global markets. On an average day, it processes futures and options trades tied to $1.5 trillion of underlying equity indexes, and interest-rate-related bets with a notional value of $9.6 trillion, according to its website.
Futures -- CME's core product -- are contracts tied to future levels of commodity prices, stock indexes, bonds and other asset values. Traders use them to hedge against volatility, or bet on market moves. Among the biggest at CME are futures tied to the S&P 500 and benchmark SOFR interest rates.
It has experienced disruptions before. In February 2019, trading across all markets on CME's electronic platform was halted for several hours due to technical problems. Other markets in the U.S. and Europe have also experienced occasional outages over the past decade.
This was the longest outage in recent CME history, but the blow was softened because it came late on Thanksgiving. The regular market action that followed on Black Friday was uneventful, much like a typical postholiday trading session.
"At least they picked a good date to have an outage," said Agustin Lebron, a trader in Prague. "If this were a normal day, this would be a very big deal."
Write to Alexander Osipovich at alexo@wsj.com and Kimberley Kao at kimberley.kao@wsj.com
(END) Dow Jones Newswires
November 28, 2025 14:34 ET (19:34 GMT)
Copyright (c) 2025 Dow Jones & Company, Inc.
Comments