Sometimes, you need to store some state (typically a key/value pair) in a step from one workflow execution and later read that state in another step from another workflow execution. There's no intrinsic key/value store in Workflows. However, you can use Firestore to store and read key/value pairs from Workflows.
In the workflow.yaml, you can see how to store different types of key/value pairs to Firestore. It uses the workflow name as the collection name and stores each key/value pair in a single document.