AWS Step Functions is a fully managed workflow service for application developers. You can think & work at a high level, connecting and coordinating activities in a reliable and repeatable way, while keeping your business logic separate from your workflow logic. After you design and test your workflows (which we call state machines), you can deploy them at scale, with tens or even hundreds of thousands running independently and concurrently. Step Functions tracks the status of each workflow, takes care of retrying activities on transient failures, and also simplifies monitoring and logging. To learn more, step through the Create a Serverless Workflow with AWS Step Functions and AWS Lambdatutorial.
Since our launch at AWS re:Invent 2016, our customers have made great use of Step Functions (my post, Things go Better with Step Functions describes a real-world use case). Our customers love the fact that they can easily call AWS Lambda functions to implement their business logic, and have asked us for even more options.