Exploring Rego ebook

Exploring Rego: Declarative policy for the modern cloud

By John Bristowe, Steve Fenton, and Matt Allford

Each day, more of us bump into Rego, the language behind Open Policy Agent. Exploring Rego is the book for that moment: a thorough, hands-on guide to the language behind Open Policy Agent, written for engineers who need to go from "what does this even do" to "I can write, test, and ship this at scale with confidence."

The book starts where you are, thinking in familiar, imperative terms, and gradually rewiring that instinct into Rego's declarative logic. You'll then be introduced to language features, along with solid advice on how to use them effectively. You'll find out all the bear traps and tar pits so you can write policy code that works. In the later stages, you'll learn how to build production-ready policies that are provably correct, scalable, and easy to maintain.

The whole book builds on a single example, so there's less time spent reading scenario set-ups and more time exploring Rego itself. By the end of the book, you'll be confident in managing the policy code that makes crucial decisions for your organization.

Publication date: July 27, 2026.

Contents at a glance

• Thinking declaratively
• Your first policies
• Values and types
• Variables and references
• Rules
• Equality and assignment
• Comprehensions
• Negation
• Quantification
• Functions
• Control flow keywords
• Built-in functions
• Modules, packages, imports
• Metadata and annotations
• Schemas and type checking
• Testing policies
• Patterns and best practices