Twitter and Mr. Musk did not respond to requests for comment.
In an email to employees on Monday, which was seen by The New York Times, Mr. Musk said the layoffs over the weekend were “a difficult organizational overhaul focused on improving future execution.” He said those still at the company would receive “very significant stock and other compensation awards” on March 24.
In the late 2000s and early 2010s, Twitter was known for regular failures and its “Fail Whale,” an image of a whale being airlifted by a flock of birds that appeared when the site did not function. Over the years, the company added hundreds of people to its infrastructure teams and improved its server technology to mitigate outages, three current and former engineers said.
After Mr. Musk took over the company, the layoffs started — followed by more substantive changes to the back-end technology. On Dec. 24, Twitter shuttered a data center in Sacramento, which had helped handle much of the web traffic to the service. That left Twitter with only two other facilities, in Atlanta and Portland, Ore.
Four days later, Twitter experienced a widespread outage, with some users getting logged out of the service or unable to view replies to their tweets.
Employee errors led to other outages. In early February, a Twitter worker deleted data from an internal service meant to prevent spam, leading to a glitch that left many people unable to tweet or to message each other, according to three people familiar with the incident.
Twitter’s engineers took several hours to diagnose the problem and restore the data stored with a backup. In that time, users received error messages that said they could not tweet because they had already posted too much. The Platformer newsletter earlier reported the cause of the problem.
A week later, an engineer testing a change to people’s Twitter profiles on Apple mobile devices caused another temporary outage. The engineer disregarded a past practice of testing new features on small subsets of users and simply rolled out the change — a tweak for Spaces, Twitter’s live audio service — to a wide swath of users, two people familiar with the move said.