apollo-server/docs/source/essentials/mutations.md

title	description
Mutations	Updating data the Apollo way

Prerequisites

• A basic understanding of a GraphQL schema (Schema)

Overview

Mutations are operations sent to the server to create, update or delete data. Those familiar with REST-based communication verbs would associate these with the PUT, POST, PATCH and DELETE methods.

• Mutations are the main entry point to make updates to the data backing Queries
• Here is what one looks like coming from the client
• Here is the corresponding server schema
• A mutation can contain arguments and fields
• Input types are passed to Apollo Server and inform it how to make the update
• The fields describe the object that is returned by a mutation, often times the object that was created or the entire collection that was modified. Or a confirmation of deletion
  • Here is what the return looks like from the previous mutation call

Actually writing resolvers for your mutations is found in server/mutations

Why mutations exist?

• Mutations exist because they have special argument types called Input types
• Input types only contain scalar types and cannot have any other input types
  • ensures that data from the client is always serializable and we don't lose any information, since circular references don't survive network call