Richly asynchronous server-less applications can be built by using AWS step functions. Choice State in AWS Step Functions is the newest feature which was long awaited.
In simply words, we define steps and their transitions and call it State Machine as a whole. In order to define this state machine, we use Amazon States Language (ASL). ASL is a JSON-based structured language that defines state machines and collections of states that can perform work (Task states), determines which state to transition to next (Choice state), and stops execution on error (Fail state).
So if the requirement is to add a branching logic like if-then-else or case statement in our state transition, then Choice state comes handy. The choice state introduces various new operators into the ASL and the sky is now limit with the possibilities. Operators for choice state include comparison operators like Is Null, IsString etc, Existence operators like Ispresent, glob wildcards where you match some string and also variable string comparison.
Choice State enables developers to simplify existing definitions or add dynamic behavior within state machine definitions. This makes it easier to orchestrate multiple AWS services to accomplish tasks. Modelling complex workflows with extended logic is now possible with this new feature.
Now one hopes that AWS introduces doing it all graphically instead of dabbling into ASL.