Composable Commerce Migration: From Magento Monolith to 21 Go Microservices

Series Hub | Next Chapter: Part 1: DDD & Bounded Contexts Decomposing Magento into 21 Services → Answer-first: Migrating from a monolithic Magento deployment to a Composable Commerce platform with 21 Go microservices eliminates $200k/year in licensing fees, boosts flash-sale concurrency capacity by 10x, and mitigates single-vendor lock-in. Starting with a Modular Monolith mindset and incrementally transitioning to Composable Commerce via 21 Go microservices, Kratos v2, and Dapr PubSub represents the definitive solution for replacing Adobe Commerce / Magento Enterprise. It delivers enterprise-grade retail capabilities (multi-warehouse routing, saga checkouts, real-time search) with $0 licensing overhead, fulfilling API-first requirements for Agentic Commerce in the 2026 AI ecosystem. ...

← Previous Chapter: Part 0: Executive Summary | Series Hub | Next Chapter: Part 2: Rush Monorepo Architecture → Answer-first: Decomposing Magento requires Domain-Driven Design (DDD) bounded contexts across 5 core domains: Catalog & Search, Order & Fulfillment, Customer & Identity, Marketing & Promotion, and Financial Accounting. Each microservice owns its private PostgreSQL database to eliminate coupling. Monolithic Magento tightly couples product catalogs, tax rules, user sessions, inventory locks, and payment processing within a single shared database. A schema change to customer addresses can inadvertently lock product catalog tables. ...

← Previous Chapter: Part 1: DDD & Bounded Contexts | Series Hub | Next Chapter: Part 3: Go + Kratos v2 Framework Deep Dive → Answer-first: Using Microsoft Rush with PNPM workspaces enables polyglot monorepo management across 21 Go microservices and 2 Next.js frontends. It automates Protobuf code generation via Buf, enforces dependency boundaries, and slashes CI build times by 70% with incremental build caching. Managing 21 independent Git repositories creates severe operational friction: version mismatch across shared Protobuf contracts, fragmented CI pipelines, and delayed end-to-end integration testing. ...

← Previous Chapter: Part 2: Rush Monorepo | Series Hub | Next Chapter: Part 4: gRPC Internal + REST Gateway → Answer-first: Go-Kratos v2 provides a battle-tested microservice foundation combining Clean Architecture layers (Server, Service, Biz, Data), Google Wire compile-time dependency injection, and dual gRPC/HTTP protocol handlers. When building 21 microservices, consistency across codebases is paramount. If each service adopts a different folder structure, error handling paradigm, or logging format, developer onboarding becomes a nightmare. ...

← Previous Chapter: Part 3: Go + Kratos v2 Framework Deep Dive | Series Hub | Next Chapter: Part 5: Migrating Magento EAV Schema to PostgreSQL → Answer-first: Every API in our Composable Commerce system starts with a Protocol Buffers (.proto) contract. Internal microservices communicate over binary gRPC for 7x faster serialization, while gRPC-Gateway automatically exposes standard REST/JSON endpoints with OpenAPI 3.1 specs for web and mobile clients. In modern 2026 cloud architectures, internal services communicate over gRPC (type-safe, binary format, ~7x faster than JSON over HTTP/1.1). External clients (web browsers, mobile apps) communicate over standard REST via a Gateway Service (using grpc-gateway or Connect by Buf running at the edge). ...

← Previous Chapter: Part 4: gRPC Internal + REST Gateway | Series Hub | Next Chapter: Part 6: Phase 1 — Strangler Fig → Answer-first: Migrating Magento’s Entity-Attribute-Value (EAV) tables (catalog_product_entity_*) to PostgreSQL eliminates 20+ SQL table joins per query. By separating static attributes (SKU, price, status) into typed relational columns and dynamic custom attributes into binary JSONB columns with GIN indexing, catalog read queries drop from 450ms to 1.2ms. 1. The Magento EAV Nightmare: Why It Collapses Under Load In Magento 2, fetching a single product requires joining across half a dozen type-specific tables: ...

← Previous Chapter: Part 5: Migrating Magento EAV Schema | Series Hub | Next Chapter: Part 7: Phase 2 — Dual-Write CDC → Answer-first: Phase 1 of the Strangler Fig migration routes catalog read traffic (/products/*, /catalog/*, /search/*) to high-speed Go microservices via Cloudflare Edge Workers while keeping Magento active for checkout. This offloads 82% of server compute load from the legacy monolith with zero downtime. flowchart TD Client["Client Browser / Mobile App"] --> Edge["Cloudflare Edge Worker (Traffic Router)"] Edge -->|"/products/* & /search/* (82% Traffic)"| GoCatalog["Go Catalog & Search Service (K8s)"] Edge -->|"/checkout/* & /customer/* (18% Traffic)"| Magento["Legacy Magento Monolith (PHP/MySQL)"] 1. Cloudflare Edge Routing Implementation // cloudflare-edge-router.ts export default { async fetch(request: Request, env: Env): Promise<Response> { const url = new URL(request.url); // Route Catalog & Search to new Go Microservices if (url.pathname.startsWith('/api/v1/products') || url.pathname.startsWith('/api/v1/search')) { return fetch(`https://catalog-api.example.com${url.pathname}${url.search}`, request); } // Fallback all other requests (Checkout, Admin) to legacy Magento return fetch(`https://legacy-magento.example.com${url.pathname}${url.search}`, request); } };

← Previous Chapter: Part 6: Phase 1 — Strangler Fig | Series Hub | Next Chapter: Part 8: Phase 3 — Full Cutover → Answer-first: Dual-writing at the application layer creates race conditions and split-brain states. Instead, Phase 2 implements Change Data Capture (CDC) via Debezium reading the MySQL binlog directly, streaming event deltas through Apache Kafka to populate PostgreSQL microservice databases asynchronously. flowchart LR MagentoAdmin["Magento Admin Update"] --> MySQL["Magento MySQL"] MySQL -->|"Binlog Stream"| Debezium["Debezium CDC Connector"] Debezium -->|"JSON Event Deltas"| Kafka["Kafka Topic: magento.catalog.products"] Kafka -->|"Consumer Group"| GoSync["Go Catalog Sync Worker"] GoSync -->|"Upsert JSONB"| Postgres["Target PostgreSQL"]

← Previous Chapter: Part 7: Phase 2 — Dual-Write | Series Hub | Next Chapter: Part 9: Transactional Outbox & Sagas → Answer-first: Phase 3 transfers write authority for Orders and Payments to the Go microservices. Once historical orders are reconciled and payment webhooks are repointed, the Magento PHP monolith is placed in read-only maintenance mode and subsequently decommissioned. The Cutover Runbook Checklist: T-24h: Run full data reconciliation audit between MySQL and PostgreSQL. T-2h: Lower DNS TTL to 60 seconds on all retail domains. T-0: Flip Cloudflare routing rule for /checkout to Go order-service. T+1h: Verify zero failed payments in Stripe / PayPal webhooks. T+48h: Terminate legacy Magento EC2 instances.

← Previous Chapter: Part 8: Phase 3 — Full Cutover | Series Hub | Next Chapter: Part 10: ADR Walkthrough — 24 Architecture Decisions → Answer-first: In a distributed e-commerce architecture without 2-Phase Commit (2PC), distributed consistency is achieved via the Transactional Outbox Pattern (saving domain events in the same SQL ACID transaction as business state) and Orchestrated Sagas (executing compensating transactions upon payment or inventory failure). sequenceDiagram autonumber actor Customer as Customer participant Order as Order Service (Saga Orchestrator) participant Inventory as Inventory Service participant Payment as Payment Service Customer->>Order: Create Order Order->>Order: Save Order (PENDING) + Outbox Event (Atomic ACID) Order->>Inventory: Reserve Stock (gRPC) alt Inventory Available Inventory-->>Order: Stock Reserved OK Order->>Payment: Authorize Payment (gRPC) alt Payment Succeeded Payment-->>Order: Payment Captured OK Order->>Order: Update Order (CONFIRMED) Order-->>Customer: Order Placed Successfully! else Payment Failed Payment-->>Order: Card Declined Order->>Inventory: Compensating Tx: Release Reserved Stock Order->>Order: Update Order (CANCELLED) Order-->>Customer: Payment Failed end else Out of Stock Inventory-->>Order: Insufficient Stock Order->>Order: Update Order (CANCELLED) Order-->>Customer: Item Out of Stock end

← Previous Chapter: Part 9: Transactional Outbox & Sagas | Series Hub Answer-first: Architecture Decision Records (ADRs) provide an immutable, version-controlled record of structural choices. This chapter documents all 24 production ADRs covering database selection (PostgreSQL + JSONB), messaging (Kafka), monorepo governance (Rush), framework (Kratos v2), and authentication (BFF + HttpOnly cookies). Summary of Key Production ADRs ADR # Decision Title Selected Option Key Trade-Off Rationale ADR-001 Primary Backend Language Golang 1.25+ Sub-millisecond startup, low memory footprint, high concurrency goroutines. ADR-002 Microservice Framework Kratos v2 Native Protobuf annotations, Google Wire compile-time DI, Clean Architecture. ADR-003 Monorepo Tooling Microsoft Rush + PNPM Strict symlink isolation, phantom dependency elimination, polyglot support. ADR-004 Primary Database PostgreSQL (JSONB) ACID compliance, JSONB GIN indexing for dynamic E-Commerce attributes. ADR-005 Event Streaming Apache Kafka High-throughput durable event log, replayability for new microservices. ADR-006 Inter-Service Transport gRPC / Protobuf Binary payload efficiency, type-safe API contracts, auto-generated SDKs. ADR-007 Client Gateway grpc-gateway Zero-maintenance REST/JSON exposure from existing Protobuf definitions. ADR-008 Distributed Transactions Saga + Outbox Eliminates blocking 2-Phase Commit locks while ensuring eventual consistency.