driver-core/src/main/com/mongodb/ReadPreference.java
public static TaggableReadPreference nearest(final List<TagSet> tagSetList,
                                                 final long maxStaleness, final TimeUnit timeUnit) {
        return new NearestReadPreference(tagSetList, maxStaleness, timeUnit);
    }
public static TaggableReadPreference nearest(final List<TagSet> tagSetList,
                                                 final long maxStaleness, final TimeUnit timeUnit) {
        return new NearestReadPreference(tagSetList, maxStaleness, timeUnit);
    }
Gets a read preference that forces reads to the primary or a secondary with one of the given sets of tags that is less stale than
the given maximum.

<p>
The driver will look for a secondary with each tag set in the given list, stopping after one is found,
or the primary if none are available.
</p>

<p>
The driver estimates the staleness of each secondary, based on lastWriteDate values provided in server isMaster responses,
and selects only those secondaries whose staleness is less than or equal to maxStaleness.
</p>

@param tagSetList the list of tag sets to limit the list of secondaries to
@param maxStaleness the max allowable staleness of secondaries. The minimum value is either 90 seconds, or the heartbeat frequency
plus 10 seconds, whichever is greatest.
@param timeUnit the time unit of maxStaleness
@return ReadPreference which reads nearest node respective of tags.
@since 3.4
@see TaggableReadPreference#getMaxStaleness(TimeUnit)