Pros
There is a strong collaborative spirit amongst the engineers and their management. Mastery hires a lot of highly experienced, dedicated individuals.
Kontras
They demand overtime work without paying for it. Contractors are pre-approved for 40 hours per week; anything beyond that must be approved in writing ahead of time. The company never approves anything beyond 40 hours, yet they regularly demand excess work. I averaged 12 hours per week of unpaid overtime while I was there.
The best employees are unceremoniously dropped, and the timing of these cuts is at the very least suspicious. My team's product manager was incredibly effective and well-liked. He took a long weekend (approved weeks in advance) to attend a wedding, and was let go the day he was supposed to return. A staff engineer was hospitalized for 4 days, and he mentioned upon returning that he may need to take some time off in the near future. They instantly canned him.
I was working with two engineers on a high priority feature that required round-the-clock efforts over a weekend. As soon as the feature was complete, our accesses were locked from all systems and the three of us were replaced with six offshore hires.
The company processes are geared toward visible metrics as opposed toward productivity. Examples: engineer performance is gauged by number of lines of code written; any production issue requires at least 10 engineers on a Zoom call until the issue is resolved, instead of letting people actually focus on solving the problem.