Distributed systems let teams ship faster, scale safely, and isolate failure. They also introduce new failure modes: partial outages, slow dependencies, data consistency trade-offs, and operational complexity. This book is a practical guide to designing and running distributed systems with Go. It covers service boundaries, networking, concurrency, APIs (REST and gRPC), messaging, caching, data consistency, resilience patterns, observability (logging, metrics, tracing), testing, containerisation, and production deployment. Each chapter includes implementation-focused examples written in idiomatic Go, with patterns you can reuse in real services.