Which service is designed to help developers coordinate application components?

AWS Step Functions is designed to help developers coordinate application components by allowing them to create complex workflows by defining the sequence of tasks that need to be completed. This service essentially acts as an orchestrator for managing the execution of various AWS services, such as AWS Lambda, while also enabling error handling, retries, and dynamic decisions in the workflow based on the outputs of previous tasks.

With AWS Step Functions, developers can visualize their application flows as state machines, making it easier to manage and monitor the coordination between different components of their applications. This service is particularly useful for microservices architectures, where multiple services need to communicate and work together in a structured manner, allowing for easier development and improved reliability.

In contrast, the other services mentioned serve different purposes: AWS Batch is focused on running large batches of computing jobs; AWS Lambda is designed for running code in response to events without provisioning servers; and AWS AppSync is utilized for building GraphQL APIs for serverless applications, which helps in data fetching and manipulation rather than coordinating tasks.