Field-level cost analysis in GraphQL - Mini Project: Build & Apply

Field-level Cost Analysis in GraphQL

📖 Scenario: You work for an online store that uses GraphQL to fetch product data. The company wants to analyze the cost impact of fetching specific fields in product queries to optimize performance and reduce server load.

🎯 Goal: Build a GraphQL query and configuration that tracks the cost of fetching each field in a product query. You will create a simple cost map, apply it to a query, and finalize the cost analysis setup.

📋 What You'll Learn

Create a GraphQL query for products with specific fields

Define a cost map for each field in the product query

Apply the cost map to calculate total query cost

Complete the cost analysis configuration

💡 Why This Matters

🌍 Real World

Companies use field-level cost analysis to optimize GraphQL queries, reducing server load and improving response times.

💼 Career

Understanding query cost helps backend developers and API designers create efficient and scalable GraphQL APIs.

1

Create the Product Query

Write a GraphQL query called productQuery that fetches id, name, and price fields from products.

GraphQL

# Write the GraphQL query named productQuery fetching id, name, and price from products
# Your code here

Need a hint?

Use backticks to create a multi-line string for the query. Include the fields exactly as id, name, and price.

2

Define Field Cost Map

Create a constant object called fieldCostMap that assigns the cost 1 to id, 2 to name, and 3 to price.

GraphQL

const productQuery = `
  query {
    products {
      id
      name
      price
    }
  }
`;

// Define fieldCostMap with costs for id, name, and price
# Your code here

Need a hint?

Create an object with keys id, name, and price and assign the costs as numbers.

3

Calculate Total Query Cost

Write a function called calculateQueryCost that takes an array of field names and returns the sum of their costs using fieldCostMap. Then, create a variable totalCost that calculates the cost of ['id', 'name', 'price'].

GraphQL

const productQuery = `
  query {
    products {
      id
      name
      price
    }
  }
`;

const fieldCostMap = {
  id: 1,
  name: 2,
  price: 3
};

// Write calculateQueryCost function and totalCost variable
# Your code here

Need a hint?

Loop over the array of fields, add each field's cost from fieldCostMap to a total, and return it.

4

Complete Cost Analysis Configuration

Create an object called costAnalysisConfig with two properties: query set to productQuery and totalCost set to the totalCost variable.

GraphQL

const productQuery = `
  query {
    products {
      id
      name
      price
    }
  }
`;

const fieldCostMap = {
  id: 1,
  name: 2,
  price: 3
};

function calculateQueryCost(fields) {
  let total = 0;
  for (const field of fields) {
    total += fieldCostMap[field] || 0;
  }
  return total;
}

const totalCost = calculateQueryCost(['id', 'name', 'price']);

// Create costAnalysisConfig object with query and totalCost
# Your code here

Need a hint?

Create an object with keys query and totalCost assigned to the existing variables.