Merge pull request #6657 from segmentio/lizkane222-patch-8

Update what-is-replay.md Replay considers and Engage section added

Author: cmastr

src/guides/what-is-replay.md

@@ -3,9 +3,7 @@ title: Replay
 plan: replay
 ---
 
-Replay takes an archived copy of your Segment data, and re-sends it to new or existing tools.
-
-On the surface this doesn't sound like much, but this can grant huge benefits to mature data systems: By archiving and replaying data, you can avoid vendor lock-in, and protect your system against data loss.
+Replay takes an archived copy of your Segment data, and re-sends it to new or existing tools providing huge benefits to mature data systems. By archiving and replaying data, you can avoid vendor lock-in, and protect your system against data loss.
 
 ## Replays for tooling changes
 
@@ -37,14 +35,40 @@ Once a replay starts, you will not see replayed events in the Event Delivery tab
 
 You can initiate replays for some or all events, but you can't apply conditional filters that exclude certain rows of data from being replayed. You can set up [destination filters](/docs/connections/destinations/destination-filters/) to conditionally filter replayed events.
 
+The destination is not required to be enabled in order for a replay to be successful, including Destination Functions.
+- The destination must be connected to the source, but can remain disabled while the replay is running.
+- Destination filters are still considered when you run replays on disabled destinations.
+- There are a few exceptions for destinations that must be enabled for the replay to be successful : Amazon S3 and Google Cloud Source (GCS).
+
 ### Replay-eligible destinations
 
 Replays are available for any destinations which support cloud-mode data (meaning data routed through Segment) and which also process timestamps. Destinations that are only available in device-mode (meaning where data is sent directly from the users' devices to the destination tool) cannot receive Replays.
 
-Not all destinations support data deduplication, so you may need to delete, archive, or otherwise remove any old versions of the data before initiating a replay. [Contact us](https://segment.com/help/contact/) if you have questions or would like help.
+Not all destinations support data deduplication, so you may need to delete, archive, or remove any older versions of the data before initiating a replay. [contact Segment support](https://segment.com/help/contact/){:target="_blank"} if you have questions or want help.
 
 ### Replays & Destination Filters
 
-Replays are subject to the [Destination Filters](/docs/connections/destinations/destination-filters/) you've configured on that destination. For example, if you request that Identify calls be included in the replay, but your destination has a Destination Filter that blocks Identify events, the filter would block all Identify events from making it to the destination. In this case, Segment would recommend that you avoid including Identify events in the replay if you know they'll be blocked by the destination filter.
+Replays are subject to the [Destination Filters](/docs/connections/destinations/destination-filters/) you've configured on that destination. For example, if you request that Identify calls be included in the replay, but your destination has a Destination Filter that blocks Identify events, the filter then blocks all Identify events from making it to the destination. In this case, Segment recommends that you avoid including Identify events in the replay if you know they'll be blocked by the destination filter.
+
+When you request a replay, Segment asks you to provide a list of the events (type and/or name) that you want included in the replay. If you specify a list of events, then Segment only includes those specified events in the replay. If you need to exclude events in your replay, [contact Segment support](https://segment.com/help/contact/){:target="_blank"}. The Segment team can help you handle filtering you're unable to do in the replay.
+
+### Replays & Engage
+
+There are two types of replays with Engage. 
+1. Replay a Profile Source's data into Engage Space, (sending a standard source's data into an Engage Space), which can be configured to send over a specified timeframe as well as the ability to specify all or only a specific subset of events by type or name.
+
+2. Replay from an Engage Space to its connected destination, (sending data from an Engage Output Source to its connected destination), which includes all the computational data (Audiences, Computed Traits, Journeys) that destination is currently configured to receive, which can be configured to send over a specified timeframe as well as the ability to specify all or only a specific subset of events by type or name. 
+
+#### Nuances to Consider for Engage Replays
+
+**1. Replay a Profile Source's data into Engage Space**
+- When a new Profile Source is connected to an Engage Space, the default option to replay the source's data seen over the past 30 days can be selected. To request a source's additional historical data be replayed to the Engage Space, contact Segment Support at [email protected] or [create a ticket](https://segment.com/docs/engage/[url](https://app.segment.com/goto-my-workspace/home?period=last-24-hours&v2=enabled&help=create-ticket)). Please see [this documentation](https://segment.com/docs/engage/quickstart/#step-3-connect-production-sources:~:text=Step%203%3A%20Connect,production%20sources.) on further details of this process and what to include in your support request.
+
+**2. Replay from an Engage Space to its connected destination**
+- Since each instance of a destination is connected to its own Engage "Output" source, that source contains events for all of the computations that destination is connected to received data from, _the list of output sources can be found under Unify > Unify Settings > Debugger_. Because of this, it's not possible to replay only a specific computation's data to the destination, you should instead consider reaching out to [Segment support]([url](https://segment.com/help/contact/)) to request a resync of that computation to its destination instead. However, if you would like to replay all failed events seen by that destination, which will encompass all connected computations, that can be achieved with a replay. 
+- Note: The replay will be sending historical data to the destination, potentially overwriting the destination with outdated data if more recent data has been sent from the computation to the destination. In this case, a resync of the computation might also be more advantageous to get the most up-to-date data resent to the destination.
+- Rate limits for replays are configurable and can be increased or decreased upon request. However, there are some destinations which have strict rate limits and cannot be configured to send data at a higher rate than what's stated within the table on [Rate limits on Engage Event Destinations](https://segment.com/docs/engage/using-engage-data/#rate-limits-on-engage-event-destinations).
 
-When you request a replay, Segment asks you to provide a list of the events (type and/or name) that you want included in the replay. If you specify a list of events, then Segment only includes those specified events in the replay. If you need to exclude events in your replay, [reach out to Segment support](https://segment.com/help/contact/){:target="_blank"}. The Segment team can help you handle filtering you're unable to do in the replay.
+#### Engage : Replay versus Resync
+- **Replay** : A replay resends all events, specific events by type or name, or failed events over a specified period of time to the destination.
+- **Resync** : A resync sends events for a computation's (Audience, Computed Trait, Journey) entire current user base to its connected destination.