Merge pull request #1716 from segmentio/DOC-228_update-journeys-bp

DOC-228 updates

Author: markzegarelli

src/personas/journeys/build-journey.md

@@ -24,6 +24,15 @@ For more information, see [Setting up your Sources](/docs/personas/quickstart/#s
 4. You should see the entry condition on the Journey Builder canvas. It may take up to 2 minutes to see the estimated number of users in the journey.
 5. Click **+** to add the next step, and view the available step types.
 
+> info ""
+> Users can enter each Journey a maximum of one time.
+
+### Use historical data for the entry step
+
+If you select the **Use historical data** option, Segment queries all historical data to set the list of users who enter the Journey when it's published. When unselected, only users who satisfy the entry condition *after* you publish will enter the Journey.
+
+Regardless of if you select **Use historical data** in the entry condition, only future events and existing trait memberships trigger subsequent journey steps.
+
 ## Available step types
 
 Journeys provide 5 step types which you can add after the entry condition.
@@ -47,7 +56,7 @@ You can add Step Names to describe the users in the true and false branch.
 Define the number of branches you want to create. Then, add a “Wait for condition” step to define the conditions for each branch.
 
 > info ""
-> Segment Journeys does not enforce branch conditions to be mutually exclusive. For more information about ensuring branch exclusivity, see [Best Practices](#).
+> Journeys does not enforce branch conditions to be mutually exclusive. For more information about ensuring branch exclusivity, see [Best Practices](#).
 
 **Send to destinations** delivers information about the journey to the selected destination. For more information, see [Send data to destinations](/docs/personas/journeys/send-data)
 

src/personas/journeys/faq-best-practices.md

@@ -37,12 +37,33 @@ To edit the steps within a published Journey, make a copy of the Journey you wis
 
 When you do this, the key used for syncing to destinations will be different from the copied Journey. Make sure you change the reference key used in the downstream destinations accordingly.
 
+### Use Traits for conditions based on historical data
+
+Aside from the entry condition, all Journey step conditions are triggered by future events and existing trait memberships. This means that event-based conditions evaluate events that have occured *after* the Journey is published.
+
+As a result, if you want to include historical events that may have occured *before* the Journey was published, create conditions based on traits, instead of events.
+
+For example, to evaluate if a user has ever used a discount code mid-Journey, create and configure a [Computed Trait](/docs/personas/computed-traits/#conditions) to select for `discount_used = true` to use in your Journey.
+
+### Use dev spaces and data warehouse destinations to test journeys
+
+Follow these best practices to test your journeys:
+
+- While in the process of configuring a journey, use dev Personas spaces to model that journey without affecting production data. 
+- Connect a data warehouse to each step of the journey to test for success or failure of that step. 
+- For early version journeys, scaffold Send to Destination steps without connecting to your production advertising or messaging destinations.
+- Verify individual users' progress through the Journey in the Personas Exploror view.
+ 
 ## Frequently asked questions
 
 ### How often do Journeys run?
 
 Journeys run in real-time, like real-time Audiences in Personas. This means that users will progress through Journeys as Segment receives new events.
 
+### How many times can a user enter one Journey?
+
+Users can enter a given journey a maximum of one time.
+
 ### What destinations does Journeys support?
 
 Journeys supports all Personas destinations, including Destination Functions. Read more in Send data to destinations.