Step Functions for workflows in AWS - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define the type of the Step Function state.

AWS

"Type": "[1]"

Drag options to blanks, or click blank then click option'

AQueue

BTask

CLambda

DBucket

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'Bucket' or 'Queue' which are AWS services but not Step Function state types.

Using 'Lambda' as a type instead of 'Task'.

The Type field in a Step Function state defines what kind of state it is. Task is used to run a unit of work.

2fill in blank

medium

Complete the code to specify the next state in the workflow.

AWS

"Next": "[1]"

Drag options to blanks, or click blank then click option'

AProcessData

BStartState

CEndState

DInitialize

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'EndState' which is usually a terminal state, not a next step.

Using 'StartState' which is the first state, not the next.

The Next field tells the Step Function which state to run after the current one. It should be the name of the next state, here ProcessData.

3fill in blank

hard

Fix the error in the state definition by completing the missing field.

AWS

"End": [1]

Drag options to blanks, or click blank then click option'

A"true"

BTrue

C"True"

Dtrue

Attempts:

3 left

💡 Hint

Common Mistakes

Putting true in quotes, making it a string instead of boolean.

Using capitalized True which is invalid in JSON.

The End field must be a boolean true without quotes to mark the final state.

4fill in blank

hard

Fill both blanks to define a Task state with a Lambda function resource and mark it as the end state.

AWS

{
  "Type": "[1]",
  "Resource": "[2]",
  "End": true
}

Drag options to blanks, or click blank then click option'

ATask

Barn:aws:s3:::mybucket

Carn:aws:lambda:us-east-1:123456789012:function:MyFunction

DChoice

Attempts:

3 left

💡 Hint

Common Mistakes

Using S3 bucket ARN as Resource instead of Lambda ARN.

Using Choice as Type which is for branching, not tasks.

The Type must be Task to run a Lambda function. The Resource is the ARN of the Lambda function.

5fill in blank

hard

Fill all three blanks to create a Choice state that routes based on a variable's value.

AWS

{
  "Type": "Choice",
  "Choices": [
    {
      "Variable": "[1]",
      "StringEquals": "[2]",
      "Next": "[3]"
    }
  ]
}

Drag options to blanks, or click blank then click option'

A$.status

BCompleted

CSuccessState

D$.result

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong JSON path for Variable.

Using a state name that does not exist for Next.

Putting values in wrong fields.

The Variable is the JSON path to check, here $.status. The StringEquals is the value to compare, Completed. The Next is the state to go to if matched, SuccessState.

Practice

1. What is the main purpose of AWS Step Functions in a workflow?

easy

A. To monitor network traffic between AWS services

B. To coordinate and manage the sequence of tasks in a workflow

C. To provide a user interface for AWS services

D. To store large amounts of data for applications

Solution

1. Step 1: Understand the role of Step Functions

   AWS Step Functions help organize and control the order of tasks in a workflow, making sure each step runs in sequence or parallel as needed.

2. Step 2: Compare with other AWS services

   Other options describe storage, UI, or monitoring, which are not the main functions of Step Functions.

3. Final Answer:

   To coordinate and manage the sequence of tasks in a workflow -> Option B

4. Quick Check:

   Step Functions = task coordination [OK]

Hint: Step Functions organize tasks step-by-step [OK]

Common Mistakes:

• Confusing Step Functions with storage services
• Thinking Step Functions provide UI
• Assuming Step Functions monitor network traffic

2. Which JSON field is required to define a task state in an AWS Step Functions state machine?

easy

A. "Timeout" specifying the maximum execution time

B. "Retry" specifying the retry policy

C. "InputPath" specifying the input data format

D. "Resource" specifying the ARN of the task to run

Solution

1. Step 1: Identify the key field for task execution

   The "Resource" field is mandatory in a task state to specify which AWS service or Lambda function to invoke.

2. Step 2: Understand other fields

   "Timeout", "InputPath", and "Retry" are optional fields that control behavior but are not required to define a task.

3. Final Answer:

   "Resource" specifying the ARN of the task to run -> Option D

4. Quick Check:

   Task state needs "Resource" [OK]

Hint: "Resource" points to the task to run [OK]

Common Mistakes:

• Confusing optional fields with required ones
• Using "Timeout" as a required field
• Forgetting to specify the task ARN

3. Given this Step Functions snippet, what is the next state after TaskA completes successfully?

{
  "StartAt": "TaskA",
  "States": {
    "TaskA": {
      "Type": "Task",
      "Resource": "arn:aws:lambda:region:123456789012:function:FunctionA",
      "Next": "TaskB"
    },
    "TaskB": {
      "Type": "Task",
      "Resource": "arn:aws:lambda:region:123456789012:function:FunctionB",
      "End": true
    }
  }
}

medium

A. TaskB

B. TaskA

C. End state

D. No next state defined

Solution

1. Step 1: Read the "Next" field of TaskA

   The JSON shows "Next": "TaskB" for TaskA, meaning after TaskA finishes, the workflow moves to TaskB.

2. Step 2: Confirm TaskB is defined

   TaskB is defined and marked with "End": true, so it is the final step after TaskA.

3. Final Answer:

   TaskB -> Option A

4. Quick Check:

   TaskA's "Next" = TaskB [OK]

Hint: Check the "Next" field for the following state [OK]

Common Mistakes:

• Assuming TaskA loops to itself
• Thinking workflow ends after TaskA
• Ignoring the "Next" field

4. You have this Step Functions state definition:

{
  "Type": "Task",
  "Resource": "arn:aws:lambda:region:123456789012:function:MyFunction",
  "Next": "NextState"
}

What is missing that could cause a failure if the Lambda function errors?

medium

A. "Catch" block to handle errors

B. "TimeoutSeconds" field to limit execution time

C. "ResultPath" to store output

D. "StartAt" field to define the first state

Solution

1. Step 1: Identify error handling in Step Functions

   Without a "Catch" block, errors from the Lambda function cause the workflow to fail immediately.

2. Step 2: Understand other fields

   "TimeoutSeconds" limits time but is optional; "ResultPath" controls output storage; "StartAt" is for the state machine root, not individual states.

3. Final Answer:

   "Catch" block to handle errors -> Option A

4. Quick Check:

   Error handling needs "Catch" [OK]

Hint: Add "Catch" to handle task errors safely [OK]

Common Mistakes:

• Confusing "TimeoutSeconds" with error handling
• Omitting "Catch" causes workflow failure on error
• Thinking "StartAt" is needed inside a task

5. You want to build a workflow that runs two Lambda functions in parallel and then proceeds only when both finish successfully. Which Step Functions state type should you use?

hard

A. Map state

B. Choice state

C. Parallel state

D. Pass state

Solution

1. Step 1: Understand the requirement for parallel execution

   Running two Lambda functions at the same time and waiting for both to finish requires a "Parallel" state.

2. Step 2: Review other state types

   "Choice" is for branching decisions, "Map" is for iterating over items, and "Pass" passes data without work.

3. Final Answer:

   Parallel state -> Option C

4. Quick Check:

   Parallel state runs tasks simultaneously [OK]

Hint: Use Parallel state to run tasks together [OK]

Common Mistakes:

• Using Choice state for parallelism
• Confusing Map state with parallel execution
• Thinking Pass state runs tasks