Read prefs improvements

source/core/read-preference.txt

@@ -40,9 +40,9 @@ read preference modes:
   If you have application servers in multiple data centers, you may
   consider having a :ref:`geographically distributed replica set
   <replica-set-geographical-distribution>` and using a non primary read
-  preference or the :readmode:`nearest`. This reduces network latency by
-  having the application server to read from a nearby secondary, rather
-  than a distant primary.
+  preference or the :readmode:`nearest`. This allows the client to read
+  from the lowest-latency members, rather than always reading from the
+  primary.
 
 - Maintaining availability during a failover.
 
@@ -82,8 +82,7 @@ read preference modes.
 
 .. include:: /includes/read-preference-modes-table.rst
 
-You can specify a read preference mode on connection objects, database
-objects, collection objects, or per-operation. The syntax for specifying
+The syntax for specifying
 the read preference mode is :api:`specific to the driver and to the
 idioms of the host language <>`.
 
@@ -115,10 +114,8 @@ behavior <replica-set-read-preference-behavior>`. See also the
 Tag Sets
 --------
 
-Tag sets allow you to specify custom :doc:`read preferences
-</core/read-preference>` and :ref:`write concerns
-<write-operations-write-concern>` so that your application can target
-operations to specific members.
+Tag sets allow you to target read operations to specific members of a
+replica set.
 
 Custom read preferences and write concerns evaluate tags sets in
 different ways. Read preferences consider the value of a tag when
@@ -133,11 +130,11 @@ You can specify tag sets with the following read preference modes:
 - :readmode:`secondaryPreferred`
 - :readmode:`nearest`
 
-Tags are not compatible with :readmode:`primary` and, in general, only
+Tags are not compatible with mode :readmode:`primary` and, in general, only
 apply when :ref:`selecting <replica-set-read-preference-behavior-member-selection>`
 a :term:`secondary` member of a set for a read operation. However, the
-:readmode:`nearest` read mode, when combined with a tag set will select
-the nearest member that matches the specified tag set, which may be a
+:readmode:`nearest` read mode, when combined with a tag set, selects
+the matching member with the lowest network latency. This member may be a
 primary or secondary.
 
 All interfaces use the same :ref:`member selection logic

source/includes/read-preference-modes-table.rst

@@ -19,5 +19,5 @@
        members but if no :term:`secondary` members are available,
        operations read from the :term:`primary`.
    * - :readmode:`nearest`
-     - Operations read from the *nearest* member of the :term:`replica
-       set`, irrespective of the member's type.
+     - Operations read from member of the :term:`replica
+       set` with the least network latency, irrespective of the member's type.