Alexia Massalin (formerly Henry Massalin) is an American computer scientist and programmer. She pioneered the concept of superoptimization,^[1][2] and designed the Synthesis kernel, a small kernel with a Unix compatibility layer that makes heavy use of self-modifying code for efficiency.^[3][4]

After high school, she was given a scholarship to the Cooper Union School of Engineering in Manhattan, where she obtained a bachelor's and master's degree.^[5][2] She went to obtain her Ph.D. in computer science from Columbia University in 1992, studying under professor Calton Pu.

In the 1980s she worked for Philon Inc., a New York start up specializing in optimizing compilers. In October 1992, Massalin joined MicroUnity as a research scientist, where she became responsible for signal-processing modules and software architecture.^[5]

Massalin's first breakthrough product came while studying at Columbia. Massalin developed Synthesis, an operating system kernel that allocated resources, ran security and low-level hardware interfaces, and created executable code to improve performance.^[2] Synthesis optimized critical operating system code using run-time information, which was a new insight previously thought impractical.^[2] To support Synthesis, Massalin invented object-like data structures called Quajects, which contain both data and code information.^[4]

Massalin is still working on broadband microprocessors.^{[citation needed]}

Her parents were Croatian refugees from Trieste. In the 1940s, they moved to Astoria, Queens, New York, where her father became a construction worker.^[2]

In a 1996 article in Wired magazine, the author Gary Andrew Poole said she "could be the Einstein of our time."^[2] She was well known for offering piggy back rides to people she met, which included notable computer scientists such as Dennis Ritchie, Ken Thompson, and artificial intelligence pioneer Marvin Minsky.^[6]