Api Gateway

Every public-facing API in the Composable Commerce Platform starts as a .proto file. The code — Go gRPC handlers, TypeScript SDK, HTTP routes, request validation, error codes — is generated from that contract. This article documents the conventions that make that system work. Answer-first: Internal services communicate via gRPC (type-safe, binary, ~7× faster than JSON over REST). External clients (browser, mobile app) use REST via the Gateway Service (port 8000). The proto file is the single source of truth for the API contract — and three proto conventions require special attention for engineers coming from Magento: the Money type (never use float for prices), cursor-based pagination (never use offset), and proto-level field validation (validation declared in the contract, not in business logic). ...

Prerequisite: Part 2 of the System Design Masterclass. Read Part 1: System Design Thinking first to understand foundational trade-off frameworks. Answer-first: L4 load balancing routes traffic by transport-layer (IP/TCP/UDP) metadata — minimal CPU overhead but limited intelligence. L7 load balancing inspects HTTP headers, paths, and cookies — enables content-based routing and advanced health checks at the cost of higher processing overhead per request. L4 vs L7 Load Balancing — The Definitive Comparison Answer-first: The fundamental difference is where in the network stack the routing decision is made. L4 (Transport Layer) routes at TCP/UDP level using IP+port tuples. L7 (Application Layer) routes at HTTP level using headers, URLs, and payloads. ...

← Previous | Series hub | Next → Chapter 6: Clarifying the Boundaries: API Gateway vs Service Mesh When your Golang application scales from dozens to hundreds of Microservices, managing communication becomes a macro-level challenge. You will constantly encounter two tightly coupled concepts: API Gateway and Service Mesh. Many engineers ask: “If I already deploy Istio (Service Mesh), do I still need Kong (API Gateway)?” The answer lies in the fundamental difference between North-South and East-West traffic. ...

Answer-first: Complete architectural blueprint of a Go 21-service e-commerce platform. Covers domain boundaries, traffic flow, and event-driven patterns. What You’ll Learn That AI Won’t Tell You Practical latency and memory metrics comparing an Envoy-based API Gateway to a custom Go reverse proxy under 100k concurrent connections. How to tune circuit breaker thresholds (go-resiliency/breaker) to prevent premature service isolation during temporary network jitters. When transitioning from a monolithic platform to a distributed microservice setup, the hardest question isn’t “How do we write the code?” — it’s “How do these moving parts talk to each other safely, and why is each boundary drawn exactly where it is?” ...