While working at Microsoft, Engstrom alongside Alex St. John and Craig Eisler was responsible for the development of DirectX, an application programming interface for Microsoft Windows that paved the way for Windows to be a viable gaming platform as well as leading into the development of the Xbox line of video game consoles.
The three revealed the new interface around April 1995 and soon named it DirectX, in part because it directly accessed the computer hardware and bypassed some of the Windows 95's APIs.
[3] Engstrom's, St. John's, and Eisler's effort to build DirectX against the resistance they faced within Microsoft led them to be called the "Beastie Boys",[1] and the subject of the book Renegades of the Empire by Michael Drummond.
[5] Engstorm had also co-founded Catalytic, a software firm based in Kirkland, Washington but using a staff of programmers from India housed on a campus named New Oroville near Hyderabad.
After leaving Microsoft again in 2014, he spent his time as a chief technology officer and adviser for a number of startups.