# What happens under the hood for a bulk index call in Elasticsearch?

**URL:** <https://discuss.elastic.co/t/what-happens-under-the-hood-for-a-bulk-index-call-in-elasticsearch/216713>\
**Category:** Elasticsearch\
**Created:** [January 27, 2020, 7:01pm UTC](https://discuss.elastic.co/t/what-happens-under-the-hood-for-a-bulk-index-call-in-elasticsearch/216713 "2020-01-27T19:01:03Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![tlandelin](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/tlandelin/32/61497_2.png) [@tlandelin](https://discuss.elastic.co/u/tlandelin)\
**Post date:** [January 27, 2020, 7:01pm UTC](https://discuss.elastic.co/t/what-happens-under-the-hood-for-a-bulk-index-call-in-elasticsearch/216713/1 "2020-01-27T19:01:04Z")

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I'm tuning my ingestion pipeline to maximize throughput. I've read through the recommendations in the reference guide about how to tune for index speed ([https://www.elastic.co/guide/en/elasticsearch/reference/master/tune-for-indexing-speed.html](https://www.elastic.co/guide/en/elasticsearch/reference/master/tune-for-indexing-speed.html))

With all the different settings to experiment with, I find myself wondering what is going on behind the scenes during a bulk index call. What stages are there, how is work divided up, and what is parallelized?

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**Author:** ![spinscale](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/spinscale/32/25011_2.png) [@spinscale](https://discuss.elastic.co/u/spinscale)\
**Post date:** [January 28, 2020, 12:01pm UTC](https://discuss.elastic.co/t/what-happens-under-the-hood-for-a-bulk-index-call-in-elasticsearch/216713/2 "2020-01-28T12:01:27Z")

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Despite its age the definitive guide might help a bit here. Take a look at [https://www.elastic.co/guide/en/elasticsearch/guide/current/distrib-multi-doc.html#bulk-format](https://www.elastic.co/guide/en/elasticsearch/guide/current/distrib-multi-doc.html#bulk-format)

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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:** [February 25, 2020, 12:01pm UTC](https://discuss.elastic.co/t/what-happens-under-the-hood-for-a-bulk-index-call-in-elasticsearch/216713/3 "2020-02-25T12:01:40Z")

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Closed on February 25, 2020, 12:01pm UTC

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