Dozens of websites went down briefly around the globe Tuesday, including CNN, The New York Times and Britain’s government home page, after an outage at the cloud computing service Fastly, illustrating how vital a small number of behind-the-scenes companies have become to running the internet.

The sites that could not be reached also included some Amazon pages, the Financial Times, Reddit, Twitch and The Guardian.

San Francisco-based Fastly acknowledged a problem just before 6 a.m. Eastern. About an hour later, the company said: “The issue has been identified and a fix has been applied.” Most of the sites soon appeared to be back online.

The company said in an emailed statement that it was a “technical issue” and “not related to a cyber attack.”

Still, major futures markets in the U.S. dipped sharply minutes after the outage, which came a month after hackers forced the shutdown of the biggest fuel pipeline in the U.S.

Fastly is a content-delivery network, or CDN. It provides vital but behind-the-scenes cloud computing “edge servers” to many of the web’s popular sites. These servers store, or “cache,” content such as images and video in places around the world so that it is closer to users, allowing them to fetch it more quickly and smoothly.

Fastly says its services mean that a European user going to an American website can get the content 200 to 500 milliseconds faster.

Internet traffic measurement by Kentik showed that Fastly began to recover from the outage roughly an hour after it struck at mid-morning European time, before most Americans were awake.

“Looks like it is slowly coming back,” said Doug Madory, an internet infrastructure expert at Kentik. He said “it is serious because Fastly is one of the world’s biggest CDNs and this was a global outage.”

Full Coverage: Technology

Brief internet service outages are not uncommon and are only rarely the result of hacking or other mischief.

Fastly stock jumped almost 11% on Tuesday as investors shrugged off the problem.

Still, the incident highlighted the relative fragility of the internet’s architecture given its heavy reliance on Big Tech companies — such as Amazon’s AWS cloud services — as opposed to a more decentralized array of companies.

“Even the biggest and most sophisticated companies experience outages. But they can also recover fairly quickly,” Madory said.

When the outage hit, some visitors trying to access CNN.com got a message that said: “Fastly error: unknown domain: cnn.com.” Attempts to access the Financial Times website turned up a similar message, while visits to The New York Times and U.K. government’s gov.uk site returned an “Error 503 Service Unavailable” message, along with the line “Varnish cache server,” which is a technology that Fastly is built on.