public VersionedKeyQuery<K, V> asOf(final Instant asOfTimestamp) {
        Objects.requireNonNull(asOfTimestamp, "asOf timestamp cannot be null.");
        return new VersionedKeyQuery<>(key, Optional.of(asOfTimestamp));
    }
Specifies the timestamp for the key query. The key query returns the record's version for the specified timestamp.
(To be more precise: The key query returns the record with the greatest timestamp &lt;= asOfTimestamp)

@param asOfTimestamp The timestamp of the query.
@throws NullPointerException if {@code asOfTimestamp} is null
streams/src/main/java/org/apache/kafka/streams/query/VersionedKeyQuery.java