DOCSP-44657-mongosync-latency-performance

Author: jmd-mongo

source/reference/mongosync/mongosync-behavior.txt

@@ -369,6 +369,26 @@ progress.
 For more information on DDL operations, see
 :ref:`txn-prod-considerations-ddl`. 
 
+Network Latency
+~~~~~~~~~~~~~~~
+
+Network latency or long physical distances between migration components
+can negatively affect sync speed. mongosync is able to send a request and 
+get a response. 
+
+Latency between ``mongosync`` and destination shards
+  For each change event that ``mongosync`` applies, ``mongosync`` does 
+  an extra roundtrip to its metadata stored on the destination.
+
+Latency between destination shards. 
+  For each change event that ``mongosync`` applies, it has to access a 
+  document that may live on a different shard. This results in many i
+  cross-shard transactions.
+
+Latency between a given destination shards’ nodes. 
+  ``mongosync`` must use majority writes, which require acknowledgement 
+  from multiple nodes within a shard.
+
 Learn More
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