Stoyan Stefanov is a Facebook engineer, ex-Yahoo, architect of the YSlow 2.0 performance tool and creator of the smush.it image optimization tool.

He's the author of the books "React: Up and Running" (O'Reilly), "JavaScript Patterns" (O'Reilly) and "Object-Oriented JavaScript" (Packt) among others.

Stoyan blogs at phpied.com and has spoken at conferences and meetups around the world (Velocity, JSConf, OSCON, Web Directions, Fronteers...). He also runs the annual "Planet Performance Calendar" publication (https://calendar.perfplanet.com/).

He spends his offline hours biking around the beach and making music (rarely at the same time though).