How do GoF patterns apply to distributed systems design?

GoF patterns provide building blocks for distributed systems patterns. Proxy directly maps to network service proxies — gRPC stubs, API gateways, and sidecars (Envoy) are remote proxies that handle serialization, retries, and timeouts transparently. Observer scales to distributed Pub/Sub (Kafka, SNS) for event-driven microservices. Command is the foundation of Command Query Responsibility Segregation (CQRS) — requests are encapsulated as command objects, enabling audit logs, event sourcing, and asynchronous processing. Facade maps to the API Gateway pattern — a single entry point that simplifies access to multiple downstream services. Chain of Responsibility maps to middleware pipelines in service meshes and API gateways (authentication, rate limiting, logging). Strategy is used for pluggable retry, circuit-breaker, and load-balancing strategies in resilience libraries like Hystrix and Resilience4j. The core insight is that network boundaries, latency, and partial failures add new dimensions that GoF patterns must address through asynchrony and fault tolerance.