AWS Step Functions
Developer Guide

Limits

AWS Step Functions places limits on the sizes of certain state machine parameters, such as the number of API actions that you can make during a certain time period or the number of state machines that you can define. Although these limits are designed to prevent a misconfigured state machine from consuming all of the resources of the system, they aren't hard limits.

Note

If a particular stage of your state machine execution or activity execution takes too long, you can configure a state machine timeout to cause a timeout event.

General Limits

Limit Description

Names in Step Functions

State machine, execution, and activity names must be 1–80 characters in length, must be unique for your account and AWS Region, and must not contain any of the following:

  • Whitespace

  • Wildcard characters (? *)

  • Bracket characters (< > { } [ ])

  • Special characters (: ; , \ | ^ ~ $ # % & ` ")

  • Control characters (\\u0000 - \\u001f or \\u007f - \\u009f).

Step Functions allows you to create state machine, execution, and activity names that contain non-ASCII characters. These non-ASCII names don't work with Amazon CloudWatch. To ensure that you can track CloudWatch metrics, choose a name that uses only ASCII characters.

Limits Related to Accounts

Limit Description

Maximum number of registered activities

10,000

Maximum number of registered state machines 10,000

Maximum number of API actions

Beyond infrequent spikes, applications can be throttled if they make a large number of API actions in a very short period of time.

Maximum request size

1 MB per request. This is the total data size per Step Functions API request, including the request header and all other associated request data.

Limits Related to State Machine Executions

Limit Description

Maximum open executions

1,000,000. Exceeding this limit will cause an ExecutionLimitExceeded error.

Maximum execution time

1 year. If an execution runs for more than the 1-year limit, it will fail with a States.Timeout error and emit a ExecutionsTimedout CloudWatch metric.

Maximum execution history size

25,000 events. If the execution history reaches this limit the execution will fail. To avoid this, see Avoid Reaching the History Limit.

Maximum execution idle time

1 year (constrained by execution time limit)

Maximum execution history retention time

90 days. After this time, you can no longer retrieve or view the execution history. There is no further limit to the number of closed executions that Step Functions retains.

Limits Related to Task Executions

Limit Description

Maximum task execution time

1 year (constrained by execution time limit)

Maximum time Step Functions keeps a task in the queue

1 year (constrained by execution time limit)

Maximum activity pollers per Amazon Resource Name (ARN)

1,000 pollers calling GetActivityTask per ARN. Exceeding this limit results in this error: "The maximum number of workers concurrently polling for activity tasks has been reached."

Maximum input or result data size for a task, state, or execution

32,768 characters. This limit affects tasks (activity or Lambda function), state or execution result data, and input data when scheduling a task, entering a state, or starting an execution.

Limits Related to API Action Throttling

Some Step Functions API actions are throttled using a token bucket scheme to maintain service bandwidth.

Note

Throttling limits are per account, per AWS Region. AWS Step Functions may increase both the bucket size and refill rate at any time. Do not rely on these throttling rates to limit your costs.

API Name Bucket Size Refill Rate per Second
CreateActivity 100 1
CreateStateMachine 100 1
DeleteActivity 100 1
DeleteStateMachine 100 1
DescribeActivity 200 1
DescribeExecution 200 2
DescribeStateMachine 200 1
DescribeStateMachineForExecution 100 1
GetActivityTask 1,000 25
GetExecutionHistory 250 5
ListActivities 100 1
ListExecutions 100 2
ListStateMachines 100 1
SendTaskFailure 1,000 25
SendTaskHeartbeat 1,000 25
SendTaskSuccess 1,000 25
StartExecutionIn US East (N. Virginia), US West (Oregon), and EU (Ireland) 1000 200
StartExecutionAll other Regions 500 25
StopExecutionIn US East (N. Virginia), US West (Oregon), and EU (Ireland) 1000 200
StopExecutionAll other Regions 500 25
UpdateStateMachine 200 1

Limits Related to State Throttling

Step Functions state transitions are throttled using a token bucket scheme to maintain service bandwidth.

Note

Throttling on the StateTransition service metric is reported as ExecutionThrottled in Amazon CloudWatch. For more information, see the ExecutionThrottled CloudWatch metric.

Service Metric Bucket Size Refill Rate per Second

StateTransitionIn US East (N. Virginia), US West (Oregon), and EU (Ireland)

5000

1000

StateTransitionAll other regions

800

400

Restrictions Related to Tagging

Be aware of these restrictions when tagging Step Functions resources.

Note

Tagging restrictions cannot be increased like other limits.

Restriction Description

Maximum number of tags per resource

50

Maximum key length

128 Unicode characters in UTF-8

Maximum value length

256 Unicode characters in UTF-8

Prefix restriction

Do not use the aws: prefix in your tag names or values because it is reserved for AWS use. You can't edit or delete tag names or values with this prefix. Tags with this prefix do not count against your tags per resource limit.

Character restrictions

Tags may only contain unicode letters, digits, whitespace, or these symbols: _ . : / = + - @

Requesting a Limit Increase

Use the Support Center page in the AWS Management Console to request a limit increase for resources provided by AWS Step Functions on a per-Region basis. For more information, see To Request a Limit Increase in the AWS General Reference.