About Us: Mark Stuart Day, Principal

Jefelex Systems is the consulting and publishing vehicle for Mark Stuart Day. Mark is a well-known expert on distributed systems and competitive analysis. He has more than thirty years of experience in the technology industry.

IMG_7322Mark was chief scientist at Riverbed Technology for nearly ten years. Since leaving Riverbed, he has been teaching at MIT. With over 30 patented inventions, he has also made technical contributions at Dropbox, Cisco, IBM, and BBN. In the early 1990’s he was lead singer of the Boston-area rock bands Anunga Runga, LawnBoy 2000, and Hop on Pop.  He received his Ph.D. in computer science from MIT. To learn more about Mark’s background and resume see www.markstuartday.com


Mark has written Bits to Bitcoin: How Our Digital Stuff Works, a book about computer systems, for people who are smart but not technical. It’s widely available in bookstores; please contact the MIT Press for information about course adoption or reprints. Mark is available for talks and panels that relate to †he book.

Consulting: Competitive

Mark’s competitive analysis work focuses on open-information technology comparison. Using publicly-available or other nonproprietary information, he develops a perspective on the technical strengths and weaknesses of competing products.

Consulting: Systems and Intellectual Property

Having spent years on patent committees at Cisco and Riverbed, Mark is familiar with processes of identifying novel aspects of computer and software systems. He can assist with selecting which inventions should be patented, as well as critiquing or refining claims. (However he is not an attorney, and cannot take the place of a properly-educated IP attorney.)

Consulting: Executive Coaching

Senior technical experts and senior managers often see the world in different ways, potentially leading to communication breakdowns, organizational dysfunctions, or worse. Because technical experts prize expertise over social graces, they may come across as prickly or difficult. In large organizations these problems are often aggravated by distance and the legacy of various mergers and acquisitions.  Mark is experienced at improving the relationships between senior technical experts and senior managers despite these challenges.