A workflow is a set of tasks executed in a certain order (sometimes with a set of conditional flows or loops). Each time that a workflow is executed, it is considered a distinct workflow execution. You pay for workflow executions when you start them (i.e. their first task becomes available for application hosts to execute) and for each 24-hour period until they are completed.

Start a Workflow Execution
  • $0.00012 per workflow execution
Until a Workflow Execution Completes
  • $0.000006 per 24 hour period that a workflow is open
Retain a Completed Workflow Execution
  • $0.000006 per 24 hour period that a workflow is retained

Until a workflow execution is completed, your worker or client machines will execute additional tasks, may add “markers” (custom workflow execution log entries), start timers, or receive signals. For each of these you pay:

Tasks, Markers, Timers and Signals
  • $0.000030 per task, signal, timer, or marker

Example Cost Calculation

To illustrate Amazon SWF pricing, consider a simple video processing application with three tasks: download a video, encode it, and store the encoded video in Amazon S3. This application is used to encode 10,000 videos, each of which comprises a unique workflow execution. The workers and deciders in this application are all running on Amazon EC2 in the AWS GovCloud (US) Region. The cost incurred for running 10,000 workflow executions of this workflow daily is $2.10 as follows:

  • $1.20 for starting 10,000 workflow executions (10,000 x $0.00012)
  • $0.90 for initiating tasks ($0.000030 per task x 3 tasks per workflow execution x 10,000 workflow executions)
  • We assume a video can be encoded and uploaded to S3 in less than 24 hours. As a result the workflow execution completes within 24 hours of being started and there is no ongoing workflow execution charge.

Let’s suppose you also want to have Amazon SWF retain information about the encoding workflow executions for 7 days after they complete. The cost for retaining information about the workflow executions is $0.42 ($0.000006 per day per execution x 7 workflow-days of retention x 10,000 workflow executions).

In total the Amazon SWF cost to coordinate the encoding and uploading of 10,000 videos and to retain information about the associated workflow executions and processing steps for 7 days is: $2.52 ($2.10 for running the workflow executions + $0.42 for retaining information on them).

Additional details about Amazon Simple Workflow Service are available at Amazon Simple Workflow Service.