According to internal records viewed by CNBC, Twitter’s full-time workforce has dwindled to about 1,300 active, working employees, including fewer than 550 full-time engineers by title. Around 75 of the company’s 1,300 employees are on furlough, including about 40 engineers.

The company’s Trust and Safety team, which makes policy recommendations, design and product changes to keep all Twitter users safe, has fewer than 20 full-time employees.

According to internal records, there are also about 1,400 non-working Twitter employees who are still being paid but are no longer expected to continue in their old roles at the social media company. Many of them quit when Elon Musk sent out a “promise” asking them to do “hardcore” work at Twitter 2.0, including long hours.

Led by Elon Musk, Twitter has slashed staff through mass layoffs, other layoffs and changes that have forced many to resign, including ending a work-from-home policy instituted under former CEO Jack Dorsey forever.

Before Musk led a $44 billion leveraged buyout of Twitter last year, Twitter’s workforce was about 7,500 employees. Layoffs were rumored internally and expected to happen regardless of whether Musk’s acquisition went through or not. However, Musk has cut Twitter staff far more than many expected — or by about 80%, according to internal notes and two employees recently speaking to CNBC.

According to an engineer who has left the company, the loss of staff and the reduction in headcount will make it more difficult to reliably maintain the service while developing new features.

This person, who asked not to be named while speaking about a previous employer, explained that the company’s code base is huge and requires knowledge of different platforms and programming languages ​​to maintain different parts of Twitter – advertising services versus the core schedule for example . Engineers’ skills, they said, are not necessarily universal. And it will be difficult to train engineers after so much institutional knowledge has been lost, this person added.

In addition to around 1,300 full-time employees, Musk has also authorized around 130 people from his other companies, including TeslaSpaceX and The Boring Company, as well as talent from venture funds and other companies to work at Twitter.

Since the Twitter acquisition, Musk has faced backlash from Tesla shareholders for being distracted, sparking political controversy on Twitter with his strategy, and selling billions of dollars in Tesla stock to fund his Twitter acquisition .

Clarification: This story has been updated to note that the 1,300 people are active, working employees at Twitter. Another 1,400 people are non-working but paid employees of Twitter.