Updates

Author: johndowns

articles/reliability/reliability-ai-search.md

@@ -6,7 +6,7 @@ author: haileytap
 ms.author: haileytapia
 ms.service: azure-ai-search
 ms.topic: reliability-article
-ms.date: 08/20/2025
+ms.date: 08/25/2025
 ms.custom: subject-reliability
 ---
 
@@ -39,6 +39,8 @@ The addition of multiple replicas allows AI Search to:
 - Handle higher indexing and query workloads.
 - Improve resiliency by attempting to provision replicas in different availability zones, if supported in your region.
 
+One replica is automatically assigned to be the *primary replica* by Azure AI Search. All write operations are performed against that replica. The other replicas are used for read operations.
+
 You can also configure the number of *partitions*, which represent the storage used by the search indexes.
 
 It's important to understand the impact of adding replicas and partitions, because they each affect read and write performance in different ways. For more information about replicas and partitions, see [Estimate and manage capacity of a search service](/azure/search/search-capacity-planning).