ADR-005: Frontend Architecture for FlowMart E-commerce Platform

Status

Approved (2024-09-05)

Context

The frontend of our current monolithic e-commerce application faces numerous challenges:

1. Performance Issues: The current server-rendered application has slow page loads and poor mobile performance.
2. Developer Productivity: Shared frontend codebase creates development bottlenecks and team dependencies.
3. Inconsistent User Experience: Different parts of the application have divergent design patterns and interaction models.
4. Limited Reusability: Components are tightly coupled to specific pages, making code reuse difficult.
5. Testing Challenges: The current codebase has limited test coverage and is difficult to test effectively.
6. Technology Constraints: Outdated technology stack limits our ability to leverage modern frontend capabilities.
7. Scalability Concerns: Our current approach doesn’t scale well with increasing development team size.
8. Mobile Experience: The responsive web approach doesn’t deliver optimal mobile experiences.

As we transition to a microservices backend architecture, we need a complementary frontend strategy that addresses these challenges while supporting our business goals of improved customer experience, faster time-to-market, and technical agility.

Decision

We will adopt a modern, component-based frontend architecture with the following key characteristics:

1. Micro-Frontend Approach:

   • Decompose the frontend into domain-aligned micro-frontends
   • Enable independent development and deployment of frontend components
   • Provide clear ownership boundaries aligned with backend microservices

2. Core Technology Stack:

   • React: Primary UI library for component development
   • Next.js: Framework for server-rendering and static generation
   • TypeScript: For type safety and improved developer experience
   • Styled Components: For component-scoped styling
   • React Query: For data fetching and state management
   • Cypress & React Testing Library: For testing

3. Design System:

   • Create a comprehensive design system with reusable UI components
   • Implement a living style guide and component documentation
   • Establish design tokens for consistent theming
   • Support multiple brands and white-labeling capabilities

4. Architecture Patterns:

   • Module Federation: For sharing components between micro-frontends
   • Composition Layer: Shell application for integrating micro-frontends
   • BFF Pattern: Backend-for-Frontend APIs for optimized data access
   • State Management: Local state when possible, shared state when necessary
   • Feature Flags: For controlled feature rollout and A/B testing

5. Performance Optimization:

   • Server-side rendering for initial page load performance
   • Client-side rendering for rich interactive experiences
   • Code splitting and lazy loading for optimized bundle sizes
   • Aggressive caching strategies for static assets
   • Optimized media delivery with responsive images and lazy loading

6. Mobile Strategy:

   • Progressive Web App (PWA) capabilities for mobile web
   • Responsive design with mobile-first approach
   • Native app shell with React Native for iOS/Android applications
   • Shared business logic between web and native through abstraction layers

Frontend Domain Decomposition

Domain	Micro-Frontend	Primary Responsibilities	Team
Product Discovery	product-browser	Product listing, search, filtering, recommendations	Catalog Team
Product Details	product-details	Product information, options, reviews, related items	Catalog Team
Shopping Cart	cart-experience	Cart management, saved items, quick checkout	Checkout Team
Checkout	checkout-flow	Multi-step checkout, address management, payment	Checkout Team
User Account	account-portal	Profile management, preferences, order history	Customer Team
Content	content-pages	CMS-managed content, landing pages, promotional content	Marketing Team
Store Locator	store-finder	Store search, maps integration, store details	Location Team
Order Management	order-tracker	Order status, tracking, returns management	Order Team

Consequences

Positive

1. Improved Development Velocity: Teams can work independently on their domains without blocking each other.

2. Better Performance: Optimized loading strategies and modern frontend practices will improve user experience.

3. Enhanced Reusability: Shared component library and design system enable consistent, reusable UI elements.

4. Independent Deployments: Micro-frontends can be deployed independently, reducing release coordination.

5. Technology Flexibility: Different domains can adopt new technologies at their own pace.

6. Better Testing: Smaller, more focused codebases are easier to test thoroughly.

7. Improved User Experience: Consistent design language and optimized interactions improve customer satisfaction.

8. Team Autonomy: Clear ownership boundaries enable teams to take full responsibility for their domains.

Negative

1. Increased Complexity: Micro-frontend architectures add operational and integration complexity.

2. Learning Curve: Teams need to adapt to new patterns and technologies.

3. Potential Duplication: Without careful governance, similar solutions may be implemented multiple times.

4. Integration Challenges: Ensuring consistent behavior across micro-frontends requires careful coordination.

5. Performance Overhead: Micro-frontend composition can introduce additional runtime overhead if not carefully managed.

6. Increased Infrastructure Needs: More sophisticated build, deployment, and monitoring infrastructure required.

7. Governance Challenges: Balancing team autonomy with architectural consistency requires active governance.

Mitigation Strategies

1. Frontend Platform Team:

   • Create a dedicated platform team to provide shared infrastructure and tools
   • Develop reusable patterns and documentation for micro-frontend implementation
   • Provide developer tooling and simplified local development experience

2. Comprehensive Design System:

   • Invest in a robust design system with clear guidelines and components
   • Create automated tools for design compliance checking
   • Regular design system sessions to ensure alignment across teams

3. Performance Budgeting:

   • Establish clear performance metrics and budgets for each micro-frontend
   • Automated performance testing in CI/CD pipeline
   • Regular performance reviews and optimization workshops

4. Developer Experience:

   • Create standardized templates and generators for new micro-frontends
   • Provide comprehensive documentation and internal training
   • Establish frontend community of practice for knowledge sharing

5. Governance Model:

   • Create a frontend architecture council with representatives from each team
   • Regular architecture reviews and pattern sharing
   • Clear guidelines for when to share vs. create new components

Implementation Details

Phase 1: Foundation (Q4 2024)

1. Create core design system and component library
2. Establish micro-frontend shell architecture
3. Develop initial build and deployment pipeline
4. Implement authentication and session management
5. Create developer documentation and examples

Phase 2: Domain Migration (Q1-Q2 2025)

1. Migrate high-priority domains to micro-frontend architecture
2. Implement analytics and monitoring strategy
3. Develop advanced patterns for cross-domain interaction
4. Enhance performance optimization capabilities
5. Create specialized mobile experiences

Phase 3: Advanced Capabilities (Q3-Q4 2025)

1. Implement personalization framework
2. Develop advanced A/B testing capabilities
3. Enhance internationalization and localization
4. Create specialized native experiences
5. Implement advanced analytics and behavior tracking

Considered Alternatives

1. Monolithic Single-Page Application (SPA)

Pros: Simpler architecture, unified codebase, shared state management
Cons: Development bottlenecks, scaling challenges, larger bundle sizes

This approach would be simpler initially but would recreate many of our current scaling challenges.

2. Server-Side Rendering Only

Pros: Simpler technology stack, better SEO by default, reduced client-side JavaScript
Cons: Limited interactivity, slower subsequent navigation, poorer offline capabilities

While this would improve initial load performance, it would limit our ability to create rich interactive experiences.

3. Native Mobile Apps Only for Mobile

Pros: Optimal mobile experience, full native capabilities, offline functionality
Cons: Development cost, platform duplication, release friction

This would deliver better mobile experiences but at significantly higher development and maintenance costs.

4. Framework-Agnostic Approach

Pros: Maximum team autonomy, best-tool-for-job flexibility
Cons: Duplication of efforts, inconsistent experiences, integration challenges

While offering maximum flexibility, this would lead to significant inconsistency and integration challenges.

References

1. Micro Frontends (Martin Fowler)
2. Module Federation (Webpack Documentation)
3. “Building Micro-Frontends” by Luca Mezzalira
4. Frontend Design Systems
5. Atomic Design by Brad Frost
6. React Documentation
7. Next.js Documentation

Decision Record History

Date	Version	Description	Author
2024-08-10	0.1	Initial draft	Jennifer Lee
2024-08-20	0.2	Added implementation phases and domain decomposition	Alex Johnson
2024-08-30	0.3	Incorporated feedback from UX and frontend teams	Sarah Chen
2024-09-05	1.0	Approved by Architecture and UX Boards	Architecture Board

Appendix A: Frontend Architecture Overview

Appendix B: Component Development Workflow

Appendix C: Micro-Frontend Integration Patterns