What is AWS Step Functions? How It Works & Use Cases

Are you tired of juggling all the pieces of your complex application? AWS Step Functions is an effective service provided by Amazon Web Services (AWS) that makes it effortless to coordinate the components of distributed applications and micro-services using visual workflows. It allows you to build, run, and visualize the components of your applications, ensuring that they are running correctly at all times.

In this blog post, we'll dive into what AWS Step Functions is and how it works. We'll also take a look at some of the most common use cases for this service, from building micro-services to processing batch jobs. So, if you're looking for a powerful tool to help you coordinate the components of your applications, read on to learn more about AWS Step Functions!

What is AWS Step Functions?

AWS Step Functions is a serverless orchestration service for modern applications that allows developers to create multi-step application workflows through a visual drag-and-drop editor. It lets users integrate with AWS Lambda functions and other AWS services so that teams can quickly put together individual micro-services into a unified workflow while they can also manage each independently. 

This AWS-managed service, in simple terms, lets developers orchestrate multiple AWS services to carry out their tasks. So you create steps in a workflow in which a step's output automatically becomes another's input. AWS Step Functions offers powerful functionalities like:

  • Managing inputs and outputs
  • Error handling
  • Automatic retry handling
  • Triggering and tracking for each step in a workflow

These functionalities reduce organizations' workload, allowing them to focus on building and scaling their business processes by ensuring that dozens of steps execute in the correct order.

What is AWS Step Functions for?

AWS Step Functions coordinates the components of distributed applications and microservices using visual workflows. It allows users to build, run, and visualize the components of their applications and can be used for a variety of tasks, such as:

  • Coordinating Microservices
  • Building Serverless Applications
  • Processing Batch Jobs
  • Error Handling and Retries
  • Monitoring and troubleshooting

We'll dive deeper into these under Use Cases later in this article.

aws step functions use cases

When should I use AWS Step Functions?

You should consider using AWS Step Functions when you have a complex application or process that needs to coordinate multiple steps or components and you want to:

1. Build, run, and visualize the components of your application

Step Functions allows you to create visual workflows that define the order of execution for your application's components, making it easy to build, test, and deploy your application.

2. Coordinate microservices

If you are building a micro-services-based application, Step Functions can help you coordinate the execution of multiple microservices, ensuring that they are executed in the correct order and under the right conditions.

3. Build serverless applications

If you are building a serverless application, Step Functions can help you trigger AWS Lambda functions and pass data between them, allowing you to build complex applications using a serverless architecture.

4. Process batch jobs

If you need to process a large number of batch jobs, Step Functions can help you coordinate the execution of these jobs, ensuring they are run in the correct order and with the correct inputs.

5. Implement error handling and retries

Step Functions provides built-in error handling and retries, making it easy to build resilient applications that can handle failures gracefully.

6. Monitor and troubleshoot

Step Functions provides a visual representation of the state of your application, making it easy to understand what's happening in your application and troubleshoot issues when they arise.

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How AWS Step Functions works

By breaking down complex workflows into manageable multi-steps and adding flow logic, AWS Step functions maintains the application state, tracks each workflow step of your application, and logs the event data exchanged between application components. In other words, if your network fails or components hang, your application will pick up where it left off. 

AWS Step Functions
Source: AWS

So, how does AWS Step Functions work?

Step Functions works based on a visual workflow, helping developers use AWS services to orchestrate micro-services, build distributed applications, create data and machine learning pipelines, and automate every process.

In order to understand how this service works, we must first tap into its key concepts.

State Machine

A state machine is a behavior model consisting of a finite number of states which is why it's also known as a Finite-State Machine (FSM). The machine executes state transitions and produces output based on the current state or a given input. Step Functions uses the term to define its workflows. In the service, it's a workflow defined using JSON text representing the individual steps (or states) in the workflow containing fields such as StartAt, TimeoutSeconds, and Version. See state machine structure for more information.

State

Now that we've defined a state machine, let's take a closer look at the definition of a "state." As briefly mentioned earlier, a state corresponds to a "step" representing individual steps in your state machine. States can be used to achieve a variety of actions.

  • Task state: performing work in the state machine
  • Choice state: choosing between different paths in a workflow
  • Fail or succeed state: stopping the workflow with fail or success
  • Pass state: Passing output or some fixed data to another state
  • Wait state: To pause the workflow for a specified amount of time
  • Parallel state: Parallel branches of execution
  • Map state: Repeat execution for each item of input

The states you choose to include in your state machine and the relationships between them are the building blocks of Steps Functions.

Task State

A task state refers to a single unit of work executed by the state machine. All work included in your state machine is carried out through tasks. A task uses an activity or an AWS Lambda function to perform work. You can use tasks to call API actions of two hundred Amazon and AWS services.

Pros and cons of AWS Step Functions

aws step functions benefits

Benefits of AWS Step Functions

Step Functions is a fully managed AWS service that provides several benefits when coordinating the components of distributed applications and micro-services:

  • Easy to use

Step Functions provides a visual interface for creating and managing workflows, making it easy to understand the components of your application and how they are related.

  • Integration with other services

Step Functions can be integrated with other AWS services such as AWS Lambda, AWS ECS, AWS SageMaker, and more, which provides great flexibility to easily build applications.

  • Simplified orchestration of multiple micro-service-based applications

Using Step Functions, you can ensure that multiple micro-services are executed in the correct order under the right conditions.

  • Increased application resilience

AWS Step Functions helps you ensure fewer user requests fail as it manages the workflow steps, errors, and restarts to perform the application tasks as expected.

  • Low code

Using Step Functions, engineers can reduce the time spent writing integration code that defines the relationship between separate application components. 

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Drawbacks of AWS Step Functions

cons of aws step functions
  • Vendor lock-in

Step Functions is an AWS-specific service, which means that it can only be used to coordinate the components of applications that are running on AWS.

  • Functional limits on the AWS side

The AWS Step Functions have various functional limitations. Data passing through your workflows is limited to 256KB, state machines are limited to one year of execution, and execution history is retained for only 90 days.

  • Harder to understand application code

Decoupling business logic from workflow logic may make your application code more difficult for others in your team to understand.

  • Limited monitoring capabilities

Although each state machine exposes data to AWS CloudWatch, it isn't sufficient for monitoring all your micro-services and functions. 

  • The complexity of Amazon States Language

The JSON-based Amazon States Language is a highly complex structured language. Learning this language can become a steep learning curve, especially considering that it won't apply to any context other than Steps Functions.

  • Cost

Although Step Functions is a pay-as-you-go service, the cost can still add up for applications with a high number of state transitions or long-running workflows.

AWS Step Functions limits

  • Limited to JSON

Step Functions only supports JSON-formatted input and output, which can be limiting for applications that need to work with other data formats.

  • Limited to execution duration

Step Functions state machines have a maximum execution duration of 1 year.

  • Limited to state machine size

Step Functions state machines have a maximum size of 1 MB and a maximum number of states of 256.

  • Limited execution event history

It has a limited execution event history quota of 25,000 entries in a workflow.

  • Limited to state machine naming

Step Functions state machines have a naming constraint, which means you can't use certain characters and special characters in the name of the state machines.

See Step Functions quotas for more information.

While AWS Step Functions is a powerful service, it is not the right solution for every use case. Considering the limitations and drawbacks is essential when evaluating whether it is the right choice for your application.

Common use cases for AWS Step Functions

Step functions use cases
Source: AWS

1. Coordinating Microservices

One of the main use cases of Step Functions is to coordinate the components of micro-services-based applications. With Step Functions, you can create visual workflows that define the order of execution for your micro-services, as well as the conditions under which they should be executed. This makes it easy to build, test, and deploy your applications, and ensures that they are running correctly at all times.

Suggested reading: AWS CloudTrail Best Practices for Security.

2. Building Serverless Applications

Another use case of Step Functions is to build serverless applications. With Step Functions, you can create workflows that trigger Lambda functions, passing data between them as necessary. This allows you to build complex applications using a serverless architecture without having to manage the underlying infrastructure.

3. Processing Batch Jobs

Step Functions can also be used to process batch jobs. By creating a workflow that defines the order of execution for a series of batch jobs, you can ensure that they are run in the correct order and with the correct inputs. This makes it easy to build, test, and deploy batch processing pipelines, and ensures that they are running correctly at all times.

4. Error Handling and Retries

Step Functions also provides built-in error handling and retries. With Step Functions, you can set retry policies for individual steps in your workflows so that if a step fails, it will be retried automatically. This makes it easy to build resilient applications that can handle failures gracefully.

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5. Monitoring and troubleshooting

Step Functions also provides a visual workflow of all the steps that have been executed, which makes it easy to understand what's happening in your application and to troubleshoot issues when they arise. With Step Functions, you can see the status of each step in your workflow, as well as the inputs and outputs of each step, which makes it easy to understand how your application is behaving.

Last but not least, the pricing

Step Functions pricing
source: AWS

Step Functions charges based on the number of state transitions required to execute your application. So, every time a step in your workflow is executed, it is counted as a state transition. AWS charges you for the total number of your state transitions across all your state machines, including retries.

  • Free Tier: 4,000 state transitions per month
  • State transitions: $0.000025 PER STATE TRANSITION after that $0.025 per 1,000 state transitions

AWS Step Functions: FAQ

1. What is the difference between Lambda and Step Functions?

AWS Lambda and AWS Step Functions are both services provided by AWS, but they serve different purposes and are typically used in different ways:

  • Purpose

Lambda is a serverless computing service that allows you to run code without provisioning or managing servers. Step Functions is a service that allows the coordination of the components of distributed applications and micro-services using visual workflows.

  • Functionality

Lambda allows you to run code on-demand in response to specific events, such as an HTTP request or a change in a data source. Step Functions enables you to create visual workflows that define the order of execution for your application's components and the conditions under which they should be executed.

  • Use cases

Lambda is typically used for running small, single-purpose functions, such as resizing images, validating user input, or running a simple data transformation. Step Functions is typically used for coordinating the components of micro-services-based applications, building serverless applications, processing batch jobs, implementing error handling and retries, and monitoring and troubleshooting.

  • Integration

Lambda can be integrated with other services such as S3, Kinesis, SNS, and SQS to perform specific actions. In contrast, Step Functions can integrate with a wide range of services such as Lambda, ECS, SageMaker, Glue, Batch, DynamoDB, SQS, and SNS to create complex workflows.

2. How does AWS Step Functions integrate with other services?

WS Step Functions integrates with several other AWS services to provide a seamless experience when building, running and visualizing the components of your applications. There are dozens of AWS services that you can integrate Step functions with, including:

  • Lambda
  • AWS Batch
  • DynamoDB
  • Amazon SNS
  • Amazon SQS
  • Amazon ECS/AWS Fargate
  • AWS Glue
  • Athena
  • Amazon EventBridge
  • API Gateway

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