﻿---
title: Controlling the user cache
description: User credentials are cached in memory on each node to avoid connecting to a remote authentication service or hitting the disk for every incoming request...
url: https://docs-v3-preview.elastic.dev/elastic/docs-content/pull/5572/deploy-manage/users-roles/cluster-or-deployment-auth/controlling-user-cache
products:
  - Elasticsearch
applies_to:
  - Elastic Stack: Generally available
---

# Controlling the user cache
User credentials are cached in memory on each node to avoid connecting to a remote authentication service or hitting the disk for every incoming request. You can configure characteristics of the user cache with the `cache.ttl`, `cache.max_users`, and `cache.hash_algo` realm settings.
<note>
  JWT realms use `jwt.cache.ttl` and `jwt.cache.size` realm settings.
</note>

<note>
  PKI and JWT realms do not cache user credentials, but do cache the resolved user object to avoid unnecessarily needing to perform role mapping on each request.
</note>

The cached user credentials are hashed in memory. By default, the Elasticsearch security features use a salted `sha-256` hash algorithm. You can use a different hashing algorithm by setting the `cache.hash_algo` realm settings. See [User cache and password hash algorithms](https://docs-v3-preview.elastic.dev/elastic/elasticsearch/tree/main/reference/elasticsearch/configuration-reference/security-settings#hashing-settings).

## Evicting users from the cache

You can use the [clear cache API](https://www.elastic.co/docs/api/doc/elasticsearch/operation/operation-security-clear-cached-realms) to force the eviction of cached users . For example, the following request evicts all users from the `ad1` realm:
```js
$ curl -XPOST 'http://localhost:9200/_security/realm/ad1/_clear_cache'
```

To clear the cache for multiple realms, specify the realms as a comma-separated list:
```js
$ curl -XPOST 'http://localhost:9200/_security/realm/ad1,ad2/_clear_cache'
```

You can also evict specific users:
```java
$ curl -XPOST 'http://localhost:9200/_security/realm/ad1/_clear_cache?usernames=rdeniro,alpacino'
```