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Didn't know AppSync could do that

AWS AppSync has the classic GraphQL API, but since last year we also have the Event API.

Challenges with REST

The frontend can access the backend through a differnt set of APIs. When using REST APIs, there's no strong standard. When using APIs from different applications, you have to deal with decentralized data management.

GraphQL

A GraphQL Schema defines the data types and relations. By design, this acts as a contract and documentation.

type Book {
    id: ID! # This is required
    title: String!
    author: String # This is optional
}

Use Subscriptions to receive a notification when an item in the backend changes.

AppSync

AWS AppSync is the managed GraphQL and pub/sub service. For datasources, it supports most of the relations and non-relational databases, a bunch of managed AWS services, HTTP endpoints and more.

Authentication

Authentication to AppSync can be done through API keys or, even better, through a Cognito integration.

type Mutation {
    @aws_auth(cognito_groups: ["group-1", "group-2"])
    createSomething()
}

AppSync Events

This is used for real-time communication and updates over websockets. Handling websockets yourself is a complex endeavour since it includes connection management, message fanout and the managing of channels. Maintaining this does not bring value, so ideally you want to use a managed service.