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Building Full Stack Applications with GraphQL

Implementing DataLoader with Apollo Server

Explore how to implement DataLoader with Apollo Server to batch multiple GraphQL requests into fewer database queries. Understand creating DataLoader instances per request, integrating them with resolvers, and improving query efficiency while avoiding caching pitfalls. This lesson guides you through enhancing backend performance with practical DataLoader usage in a full stack GraphQL application.

We'll cover the following...

Our GraphQL backend is sending too many small individual requests, uncovering an important performance issue. We’d like to batch these requests together to reduce the number of queries and improve our application’s performance.

We’ll see how we can use a DataLoader library with Apollo Server and significantly optimize our application in this lesson.

Using DataLoader

To use the DataLoader library, we first need to add it to our project.

npm install --save dataloader

The library functionality is implemented in the DataLoader type, allowing the batching of multiple queries in a single request. We need to specify how to fetch data in our application. To do this, we need to create an instance of DataLoader and pass a function that can fetch multiple objects given a list of keys.

Javascript (babel-node)
const categoriesLoader = new DataLoader(async (keys) => {
  // Fetch all categories at once
  // we will implement this later
})

We have to define DataLoaders for categories and users collections since we want to batch requests to these collections. We don’t need to create a DataLoader for the products collection because we already fetched all products with a single query.

Once we have a DataLoader instance, we can use one of the few methods to load an object from a database:

  • load(key): Load a
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