Elasticsearch best practice: aliases

📅 Published: Apr 1, 2025 • Thomas Queste

Elasticsearch aliases are a best practice. They simplify alot management of indices, for example, migration between indices.

TL;DR

An alias is simply a secondary name for an index or a set of indices
Switch underlying indices without changing application code
Switches are atomic = no zero downtime

Tips

Use the alias in application code (my_index) and target indices version-based (my_index_v1, my_index_v2) or time-based (my_index_2024, my_index_2025)
List aliases, sorted by name: GET _cat/aliases?v&s=alias
Actions done in a single calls to POST _aliases are atomic (all-performed at once)

Typical usage

Given your app only knows the alias (my_index),
Create a new index (my_index_v2) and reindex the old to the new index (my_index_v1 to my_index_v2). Then switch the alias when and only if the operation succeeds.
No change in application code, no downtime.

POST _aliases
{
  // Atomic operation (all at once)
  "actions": [
    {
      "add": {
        "index": "my_index_v2",
        "alias": "my_index"
      }
    },
    {
      "remove": {
        "index": "my_index_v1",
        "alias": "my_index"
      }
    }
  ]
}

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