How Gmail Built Security at Scale

Gmail protects over 1.8 billion users from spam, phishing, and malware every day. But building security at this scale wasn’t straightforward—it required innovative approaches to both detection and response.

The Challenge

When you’re processing billions of emails daily, traditional security approaches simply don’t work. Every decision must be made in milliseconds, and false positives affect millions of users.

The Approach

The team applied several principles from this book:

1. Tracer Bullets: Started with simple heuristics, then layered in machine learning
2. Blitz-Scale: Built systems that could handle exponential growth
3. Know When to Call It: Deprecated approaches that couldn’t scale

Full case study available in the book.