# Elastic is\_write\_index vs index\_routing in alias **URL:** \ **Category:** Elasticsearch\ **Created:** [August 23, 2020, 12:41pm UTC](https://discuss.elastic.co/t/elastic-is-write-index-vs-index-routing-in-alias/246017 "2020-08-23T12:41:35Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![Altiano\_Gerung](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/altiano_gerung/32/38040_2.png) [@Altiano\_Gerung](https://discuss.elastic.co/u/Altiano_Gerung)\ **Post date:** [August 23, 2020, 12:41pm UTC](https://discuss.elastic.co/t/elastic-is-write-index-vs-index-routing-in-alias/246017/1 "2020-08-23T12:41:35Z")
It seems like alias has the same feature with two different names, What is the different between this two actually? When to use one over the other? ---
**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:** [August 25, 2020, 1:42am UTC](https://discuss.elastic.co/t/elastic-is-write-index-vs-index-routing-in-alias/246017/2 "2020-08-25T01:42:54Z")
`is_write_index` directs **writes** to a specific index. `index_routing` directs **reads** to specific indices. ---
**Author:** ![Altiano\_Gerung](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/altiano_gerung/32/38040_2.png) [@Altiano\_Gerung](https://discuss.elastic.co/u/Altiano_Gerung)\ **Post date:** [August 25, 2020, 3:16pm UTC](https://discuss.elastic.co/t/elastic-is-write-index-vs-index-routing-in-alias/246017/3 "2020-08-25T15:16:57Z")
so what is the different between `search_routing` and `index_routing` then? ---
**Author:** ![Altiano\_Gerung](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/altiano_gerung/32/38040_2.png) [@Altiano\_Gerung](https://discuss.elastic.co/u/Altiano_Gerung)\ **Post date:** [August 30, 2020, 9:09am UTC](https://discuss.elastic.co/t/elastic-is-write-index-vs-index-routing-in-alias/246017/4 "2020-08-30T09:09:24Z")
so what is the different between `search_routing` and `index_routing` then? ---
**Author:** ![Christian\_Dahlqvist](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/christian_dahlqvist/32/4617_2.png) [@Christian\_Dahlqvist](https://discuss.elastic.co/u/Christian_Dahlqvist)\ **Post date:** [August 30, 2020, 9:27am UTC](https://discuss.elastic.co/t/elastic-is-write-index-vs-index-routing-in-alias/246017/5 "2020-08-30T09:27:59Z")
The `is_write_index` specifies which index a document is written to when written to the alias. Once written to the index it may go into any shard. I believe ILM uses this to direct all new data written to the latest index while allowing all indices to be searched. The `search_routing` and `index_routing` settings are related in that they set a specific routing value when data is written or retrieved through the index. This makes all related data accessed through the alias go to the same shard within the index. This can be sued ina multi-tenant environment where each user accesses data through an alias and all data can be concentrated into a single shard per index. This means fewer shards need to be queried when the alias is used which can help with performance. ---
**Author:** ![Altiano\_Gerung](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/altiano_gerung/32/38040_2.png) [@Altiano\_Gerung](https://discuss.elastic.co/u/Altiano_Gerung)\ **Post date:** [August 31, 2020, 1:17am UTC](https://discuss.elastic.co/t/elastic-is-write-index-vs-index-routing-in-alias/246017/6 "2020-08-31T01:17:55Z")
I see.. so routing is all about shards. that's where I got confused. Thanks Christian. ---
**Author:** ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)\ **Post date:** [September 28, 2020, 1:18am UTC](https://discuss.elastic.co/t/elastic-is-write-index-vs-index-routing-in-alias/246017/7 "2020-09-28T01:18:19Z")
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