Step Functions and Lambda architecture

1. Make coordination explicit

An order requires validation, payment, and fulfillment. You want to see each stage and its result.

Which service models the workflow?

AWS Step Functions.

A state machine represents work and transitions. Individual tasks can use Lambda or supported service integrations.

The workflow makes validation, payment, and fulfillment separate states.

Validate → Charge → Fulfill
Each state has explicit input, output, and transition behavior.

2. Choose a branch

Validation returns valid=false. The order must go to a rejection path rather than payment.

Which state type selects the next path?

A Choice state.

Choice states branch using data. Model the rejection path explicitly.

Invalid orders bypass payment and follow the rejection path.

Choice: valid?
  true  → Charge
  false → Reject

3. Repair an endless retry

A payment call occasionally times out. Retrying forever could duplicate work and hide a persistent failure.

What is a better recovery design?

Bounded retries, idempotent payment handling, and a Catch path.

Retries need limits and safe side effects. Catch routes failures that remain after retry handling.

The workflow retries transient failures, then routes unresolved errors to recovery.

Retry: selected transient errors, backoff, finite attempts
Catch: remaining error → recovery state

Practice, then check your understanding

In the interactive tour, make each decision before seeing the outcome. Wrong answers receive coaching, and replay gives you a fresh attempt without duplicating earned XP.

Read the official AWS documentation for service behavior and production details.