SWF - Simple Workflow Service

• Allows us to build workflows used to coordinate activities over distributed components (example: order flow)
• Allows to build complex, automated and human involved workflows
• It is the predecessor of Step Functions, it uses instances/servers
• It allows the usage of the same patterns/anti patterns like long running workflows
• AWS recommends defaulting to Step Functions instead of SWF, use SWF only if there is very specific workflow that requires it
• Workflow: set of activities that carry out some objective together with the logic that coordinates the activities
• Within workflows we have activity task and activity workers
• A worker is program that we create to perform tasks
• Workflows have deciders, applications that run on an unit of compute of AWS
• Deciders schedule activity tasks, provides input data to activity workers, processes events and ends the workflow when the object is completed
• SWF workflows can run for max 1 year

SWF vs Step Functions

• Default: Step Functions - they are serverless, they require lower admin overhead
• AWS FLow Framework - way of defining workflows supported by SWF
• External Signals to intervene in process, we need SWF
• Launch child flows and have the processing return to parent, we need ot use SWF
• Bespoke/complex decision logic: use SWF (custom decider application can be coded by us, we can implement whatever logic we want)
• Mechanical Turk integration: use SWF (suggested AWS architecture)