# Index template and JVM usage

**URL:** <https://discuss.elastic.co/t/index-template-and-jvm-usage/249071>\
**Category:** Elasticsearch\
**Created:** [September 18, 2020, 8:14am UTC](https://discuss.elastic.co/t/index-template-and-jvm-usage/249071 "2020-09-18T08:14:18Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![probson](https://avatars.discourse-cdn.com/v4/letter/p/e47c2d/32.png) [@probson](https://discuss.elastic.co/u/probson)\
**Post date:** [September 18, 2020, 8:14am UTC](https://discuss.elastic.co/t/index-template-and-jvm-usage/249071/1 "2020-09-18T08:14:18Z")

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Hi,

We have a number of indexs for devices with limited static fields, ie a firewall. (assuming an upgrade of the device does not add more fields)

I typically use the ECS as the template for the indexs. Would there be any performance gains to JVM usage if i created my own templates with the required fields?

Thanks

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<div class="post-metadata">

**Author:** ![warkolm](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/warkolm/32/39224_2.png) [@warkolm](https://discuss.elastic.co/u/warkolm)\
**Post date:** [September 20, 2020, 9:36pm UTC](https://discuss.elastic.co/t/index-template-and-jvm-usage/249071/2 "2020-09-20T21:36:21Z")

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Static mappings are more efficient, yes. Whether that makes a noticeable gain though, you'd want to test with your cluster and data.

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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:** [October 18, 2020, 9:36pm UTC](https://discuss.elastic.co/t/index-template-and-jvm-usage/249071/3 "2020-10-18T21:36:25Z")

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