Human Agency in a Digital World

This may be the first true AI-era self-help book—not because we need help using technology, but because we need help using it well. It's about building the knowledge—and the confidence—to question, to evaluate, to choose. Because understanding how algorithms work is the first step in making sure they work for us.
Human Agency in a Digital World is a book about reclaiming our role—not as passengers, but as pilots—in the fast-moving journey of technological change. Written by a computer scientist who is also a father, a teacher, and a lifelong student of how things work, this book is a deeply personal and accessible guide to the systems shaping our lives—and how we might shape them back.
We are surrounded by digital agents. They suggest the next song, answer our questions, sort our emails, recommend what to watch, and—often invisibly—shape what we think. But what do we know about them? And how much power do we really have to question, understand, or even redirect their impact?
In this book, Marcus Fontoura explores the hidden architectures of modern life—from social media and search engines to cloud computing, AI, and quantum technologies—uncovering both how they work and what they mean. Drawing from decades of experience building the backbone of the internet and cloud platforms, he demystifies the core concepts that govern today's systems and offers readers a way to develop digital fluency without needing a computer science degree.
But this is not just a book about machines. It's a book about people-about how we use efficiency not just to optimize for speed or cost, but to unlock creativity, opportunity, and well-being. With examples ranging from broken playlists to protein folding, and reflections that move fluidly between systems thinking and everyday life, Digital Agency asks us to consider a simple but profound question: what do we want technology to do for us, and what will we do with it in return?

Marcus Fontoura is currently in his second tenure as Technical Fellow and Corporate Vice President at Microsoft, where he works as CTO for Azure Core.
Most recently, he was the CTO at Stone (2022-2025), where he led the engineering organization, focused on building highly efficient financial platforms and an amazing engineering culture. He continues to serve as an advisor to the company.
Previously, in his first tenure as Technical Fellow and Corporate Vice President at Microsoft (2013-2022), Marcus worked as the chief architect for Azure Compute and led the Azure efficiency team. Marcus also had posts at Google, Yahoo, and IBM Research.