The company had about 7,500 employees before Musk arrived, but now has about 1,300 people, fewer than 550 of whom are full-time engineers.
Musk has also brought about 130 people from his other companies to work at Twitter, including Tesla, SpaceX and The Boring Co.
A former Twitter engineer admitted that the remaining engineers at the company are very busy and will struggle to keep the social network running as new products are added.
Twitter’s trust and security team, which makes recommendations on the social network’s policy, design and product changes to keep all users safe, has been reduced to fewer than 20 full-time employees.
Twitter also has about 1,400 unemployed employees who are still being paid but are not expected to return to their former jobs, the social network’s internal records show.
Twitter has been downsizing significantly under Musk, both through mass layoffs and changes that have prompted many to leave. One of those changes was the move away from remote work, which was introduced under previous Twitter CEO Jack Dorsey.