# Cross Cluster Search - Limits/Upgrades

**URL:** <https://discuss.elastic.co/t/cross-cluster-search-limits-upgrades/142411>\
**Category:** Elasticsearch\
**Created:** [July 31, 2018, 4:21pm UTC](https://discuss.elastic.co/t/cross-cluster-search-limits-upgrades/142411 "2018-07-31T16:21:06Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![aewhite](https://avatars.discourse-cdn.com/v4/letter/a/6de8d8/32.png) [@aewhite](https://discuss.elastic.co/u/aewhite)\
**Post date:** [July 31, 2018, 4:21pm UTC](https://discuss.elastic.co/t/cross-cluster-search-limits-upgrades/142411/1 "2018-07-31T16:21:06Z")

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I am researching rolling out multiple clusters and using Cross Cluster Search when needed. However, there are a few open question that don't seem to be addressed in the [official documentation](https://www.elastic.co/guide/en/elasticsearch/reference/current/modules-cross-cluster-search.html) yet.

1. How should upgrades be handled?
2. Can a 5.x cluster talk to a 6.x cluster or is the reverse true?
3. Are there any practical limits to the number of remote clusters that can be connected to? (10, 100, 1000?)
4. Are there any practical limits to the number of shards that can be queried in a single request?

Cross cluster search looks promising but I want to make sure that we have reasonable upgrade plans in place and practical performance expectations.

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**Author:** ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)\
**Post date:** [August 28, 2018, 4:21pm UTC](https://discuss.elastic.co/t/cross-cluster-search-limits-upgrades/142411/2 "2018-08-28T16:21:10Z")

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