backend-patterns

Backend Development Patterns

Backend architecture patterns and best practices for scalable server-side applications.

When to Activate

• Designing REST or GraphQL API endpoints
• Implementing repository, service, or controller layers
• Optimizing database queries (N+1, indexing, connection pooling)
• Adding caching (Redis, in-memory, HTTP cache headers)
• Setting up background jobs or async processing
• Structuring error handling and validation for APIs
• Building middleware (auth, logging, rate limiting)

API Design Patterns

RESTful API Structure

// PASS: Resource-based URLs
GET    /api/markets                 # List resources
GET    /api/markets/:id             # Get single resource
POST   /api/markets                 # Create resource
PUT    /api/markets/:id             # Replace resource
PATCH  /api/markets/:id             # Update resource
DELETE /api/markets/:id             # Delete resource

// PASS: Query parameters for filtering, sorting, pagination
GET /api/markets?status=active&sort=volume&limit=20&offset=0

Repository Pattern

// Abstract data access logic
interface MarketRepository {
  findAll(filters?: MarketFilters): Promise<Market[]>
  findById(id: string): Promise<Market | null>
  create(data: CreateMarketDto): Promise<Market>
  update(id: string, data: UpdateMarketDto): Promise<Market>
  delete(id: string): Promise<void>
}

class SupabaseMarketRepository implements MarketRepository {
  async findAll(filters?: MarketFilters): Promise<Market[]> {
    let query = supabase.from('markets').select('*')

    if (filters?.status) {
      query = query.eq('status', filters.status)
    }

    if (filters?.limit) {
      query = query.limit(filters.limit)
    }

    const { data, error } = await query

    if (error) throw new Error(error.message)
    return data
  }

  // Other methods...
}

Service Layer Pattern

// Business logic separated from data access
class MarketService {
  constructor(private marketRepo: MarketRepository) {}

  async searchMarkets(query: string, limit: number = 10): Promise<Market[]> {
    // Business logic
    const embedding = await generateEmbedding(query)
    const results = await this.vectorSearch(embedding, limit)

    // Fetch full data
    const markets = await this.marketRepo.findByIds(results.map(r => r.id))

    // Sort by similarity
    return markets.sort((a, b) => {
      const scoreA = results.find(r => r.id === a.id)?.score || 0
      const scoreB = results.find(r => r.id === b.id)?.score || 0
      return scoreA - scoreB
    })
  }

  private async vectorSearch(embedding: number[], limit: number) {
    // Vector search implementation
  }
}