# How does bulk API utilize active threads of write thread pool?
**URL:** https://discuss.elastic.co/t/how-does-bulk-api-utilize-active-threads-of-write-thread-pool/185444
**Category:** Elasticsearch
**Created:** [June 12, 2019, 2:35pm UTC](https://discuss.elastic.co/t/how-does-bulk-api-utilize-active-threads-of-write-thread-pool/185444 "2019-06-12T14:35:25Z")
**Posts on this page:** 5
**Page:** 1
### Author:  [@NairitiSharma](https://discuss.elastic.co/u/NairitiSharma)
#### Post date: [June 12, 2019, 2:35pm UTC](https://discuss.elastic.co/t/how-does-bulk-api-utilize-active-threads-of-write-thread-pool/185444/1 "2019-06-12T14:35:25Z")
How does bulk API utilize active threads of thread pool? I have an index with 1 shard and 1 replica. When I push , say 100 documents, using bulk API to this index, will it employ 1 thread of write thread pool to do the ingests?
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### Author:  [@DavidTurner](https://discuss.elastic.co/u/DavidTurner)
#### Post date: [June 13, 2019, 6:36am UTC](https://discuss.elastic.co/t/how-does-bulk-api-utilize-active-threads-of-write-thread-pool/185444/2 "2019-06-13T06:36:32Z")
Roughly speaking, yes, each bulk request is processed by a single `write` thread on each shard.
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### Author:  [@NairitiSharma](https://discuss.elastic.co/u/NairitiSharma)
#### Post date: [June 13, 2019, 6:52am UTC](https://discuss.elastic.co/t/how-does-bulk-api-utilize-active-threads-of-write-thread-pool/185444/3 "2019-06-13T06:52:07Z")
My indexes have 1 shard and 1 replica. Does this mean one thread will write to both the primary shard and its replica?
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### Author:  [@DavidTurner](https://discuss.elastic.co/u/DavidTurner)
#### Post date: [June 13, 2019, 8:05am UTC](https://discuss.elastic.co/t/how-does-bulk-api-utilize-active-threads-of-write-thread-pool/185444/4 "2019-06-13T08:05:40Z")
No, that can't happen: the primary and the replica are on different nodes, so they are in different processes and normally on different machines. There's no way that a single thread can do both writes.
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### Author:  [@system](https://discuss.elastic.co/u/system)
#### Post date: [July 11, 2019, 8:05am UTC](https://discuss.elastic.co/t/how-does-bulk-api-utilize-active-threads-of-write-thread-pool/185444/5 "2019-07-11T08:05:44Z")
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