# Ccs\_minimize\_roundtrips error when using 7.X high level REST API to access 6.x index

**URL:** <https://discuss.elastic.co/t/ccs-minimize-roundtrips-error-when-using-7-x-high-level-rest-api-to-access-6-x-index/194095>\
**Category:** Elasticsearch\
**Created:** [August 6, 2019, 8:06pm UTC](https://discuss.elastic.co/t/ccs-minimize-roundtrips-error-when-using-7-x-high-level-rest-api-to-access-6-x-index/194095 "2019-08-06T20:06:11Z")\
**Posts on this page:** 1\
**Showing post:** 3

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**Author:** ![iti](https://avatars.discourse-cdn.com/v4/letter/i/b19c9b/32.png) [@iti](https://discuss.elastic.co/u/iti)\
**Post date:** [August 9, 2019, 6:18pm UTC](https://discuss.elastic.co/t/ccs-minimize-roundtrips-error-when-using-7-x-high-level-rest-api-to-access-6-x-index/194095/3 "2019-08-09T18:18:50Z")

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Thanks Luca.  
I am using 6.8 REST API with 7.2 ES lib now. But got another error which reported on

> [@java.lang.ClassNotFoundException: org.elasticsearch.search.aggregations.metrics.cardinality.ParsedCardinality](https://discuss.elastic.co/t/java-lang-classnotfoundexception-org-elasticsearch-search-aggregations-metrics-cardinality-parsedcardinality/194304):
>
> My environment: two ES clusters: one ES 6.7 and one ES 7.1 My app need to use High Level REST Client to access both cluster at the same time. When I am using 7.x REST CLIENT with 7.X ES library. When accessing 6.x ES, I got [Ccs\_minimize\_roundtrips error when using 7.X high level REST API to access 6.x index](https://discuss.elastic.co/t/ccs-minimize-roundtrips-error-when-using-7-x-high-level-rest-api-to-access-6-x-index/194095) When I am using 6.x REST CLient with 7.X ES, when accessing 7.x ES,I got java.lang.ClassNotFoundException: org.elasticsearch.search.aggregations.metrics.cardinality.ParsedCardinality sinc…

Any advice? Thanks

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