How to create and manage index templates in Elasticsearch

In Elasticsearch, index templates apply predefined settings and mappings to newly created indices matching certain patterns. This approach ensures consistency, reduces configuration overhead, and minimizes indexing errors.

Using templates allows setting default shard counts, analyzers, and field mappings, making it simpler to maintain standardized data structures at scale. Adjusting a template updates defaults for future indices without affecting existing ones.

By implementing templates, organizations establish reliable patterns that simplify environment management, boost efficiency, and maintain predictable index configurations over time.

1. Identify index name patterns that trigger template application.
2. Create a template with a PUT request, defining settings, mappings, and patterns.

   $ curl --request PUT --header "Content-Type: application/json" --data '{
     "index_patterns": ["logs-*"],
     "settings": {
       "number_of_shards": 1
     },
     "mappings": {
       "properties": {
         "message": { "type": "text" }
       }
     }
   }' http://localhost:9200/_template/my_template
   
   {"acknowledged":true}

   Templates automatically apply to new indices matching logs-*.

3. Verify the template’s existence.

   $ curl --request GET http://localhost:9200/_template/my_template
   {"my_template": {...}}

   Check templates regularly to ensure ongoing relevance.

4. Use the cat templates API for a quick overview of all configured templates.

   $ curl --request GET http://localhost:9200/_cat/templates?v
   name        index_patterns order ...
   my_template logs-*         0     ...

5. Update or delete the template as requirements evolve.

   $ curl --request DELETE http://localhost:9200/_template/my_template
   {"acknowledged":true}

   Removing a template affects only future indices, not existing ones.

6. Confirm new indices match the template’s settings and mappings after creation.

   Consistent index configurations simplify queries and reduce maintenance overhead.