Step Functions and AppSynch

Question 1

What is the execution duration for a Standard vs Express Step Function?

Answer 1

Express: 5 minutes
Standard: 1 Year

Question 2

Why would you use a standard over an express step function (or vice-a-versa)

Answer 2

Standard Workflows are ideal for long-running, durable, and auditable workflows. They can run for up to a year and you can retrieve the full execution history using the Step Functions API, up to 90 days after your execution completes.

Express Workflows are ideal for high-volume, event-processing workloads such as IoT data ingestion, streaming data processing and transformation, and mobile application backends.

Question 3

Which step function type executes on:

1. at-most-once model
2. at-least-once model

And what do these mean?

Answer 3

Standard: at-most-once meaning the function will not execute more than once (unless retries are configured)

Express: possibility that an execution might be run more than once

Question 4

If a state in a step function fails, what is the default behaviour?

Answer 4

The default behaviour is to fail the function if a single stage fails.

Question 5

What two ways can we recover from a stage error in a step function?

Answer 5

We can either retry on fail (using exponential backoff) or we can catch the error and handle it and move on.

Question 6

I have an ETL job which has been transitioned to lambda to take advantage of a serverless platform. The job requires multiple processing stages which I need to orchestrate so that when one process finishes, the next one starts. Execution time for each process can vary between 1 and 8 minutes. What technology would I use and why?

Answer 6

Step functions would be ideal to orchestrate the various lambda processes. Standard step functions would be required as these have a maximum execution time of one year vs 5 minutes for express functions.