GraphQL is an open-source query language for APIs and a runtime for executing those queries with existing data. It allows clients to request specific data from the server, enabling more efficient and flexible data fetching compared to traditional REST APIs. To understand the difference between GraphQL and REST, you can check this fantastic video from ByteByteGo.
Apollo is a comprehensive GraphQL platform that consists of multiple components, including Apollo Client for managing data in the client-side application, Apollo Server for building GraphQL servers, and Apollo Studio for monitoring and managing GraphQL APIs. Apollo simplifies the development of GraphQL-based applications by providing tools and libraries that streamline data fetching, caching, and state management. It offers powerful features like real-time updates, optimistic UI, and seamless integration with various frontend frameworks.
When working with Apollo GraphQL, understanding the various fetch policies can greatly impact how data is fetched and cached. Apollo Client provides different fetch policies that determine how queries are executed and how data is stored in the cache. In this article, we’ll explore the different fetch policies in Apollo GraphQL and their use cases.
The cache-first fetch policy is the default behavior in Apollo Client. It first checks the cache for the requested data and returns the cached results if available. If the data is not present in the cache, Apollo Client makes a network request to fetch the data from the server and stores it in the cache for future use. Subsequent requests for the same data will be served from the cache unless the data expires or is invalidated.
const { data } = useQuery(GET_USER_DETAILS, { fetchPolicy: 'cache-first' });The cache-and-network fetch policy is similar to cache-first, but with an additional network request. Apollo Client first checks the cache and returns any available data. It then proceeds to make a network request to fetch the latest data from the server. Once the response is received, Apollo Client updates the cache with the new data. This fetch policy is useful when you want to display cached data immediately while ensuring it stays up to date.
const { data } = useQuery(GET_USER_DETAILS, { fetchPolicy: 'cache-and-network' });The network-only fetch policy skips the cache entirely at the first time and always makes a network request to fetch fresh data from the server. The response is stored in the cache. This fetch policy is suitable when you require real-time or dynamic data, therefore it prioritizes consistency with server data.
const { data } = useQuery(GET_USER_DETAILS, { fetchPolicy: 'network-only' });The cache-only fetch policy solely relies on the cache and does not make any network requests. If the requested data is present in the cache, it is returned. However, if the data is not found in the cache, Apollo Client returns an error. This fetch policy is useful when you want to strictly work with cached data and avoid any network requests.
const { data } = useQuery(GET_USER_DETAILS, { fetchPolicy: 'cache-only' });The no-cache fetch policy bypasses the cache entirely and always makes a network request to fetch the data from the server. However, unlike network-only, the response is not stored in the cache. This fetch policy is suitable when you want to fetch fresh data from the server but do not want to store it in the cache.
const { data } = useQuery(GET_USER_DETAILS, { fetchPolicy: 'no-cache' });The standby fetch policy is similar to cache-first but with a subtle difference. This query doesn’t automatically update when underlying field values change. You can manually update this query by using refetch and updateQueries. At the time of writing, I haven’t used this policy yet.
Understanding the various fetch policies in Apollo GraphQL is crucial for optimizing data fetching and caching in your applications. Each fetch policy provides a different behavior to balance between using cached data and fetching fresh data from the server. By selecting the appropriate fetch policy, you can improve performance, reduce unnecessary network requests, and ensure data consistency.
Remember to consult the Apollo Client documentation for more detailed explanations and examples of using fetch policies in Apollo GraphQL.
Disclaimer: The author generated this text in part with GPT-3, OpenAI’s large-scale language-generation model. Upon generating draft language, the author reviewed, edited, and revised the language to their own liking and takes ultimate responsibility for the content of this publication. At first, GPT-3 generated some wrong answers and I had to check the documentation to guarantee that all the information was right.
