Delay when fetching data from headless-admin-user/v1.0/user-accounts for the first time after server restart

Issue

When running a REST API call as below:
```
/o/headless-admin-user/v1.0/user-accounts/fields=id,familyName,givenName,jobTitle,organizationBriefs.name,image,emailAddress,profileURL,contactInformation.telephones.phoneNumber,contactInformation.telephones.phoneType,customFields&pageSize=1000
```
Portal users and administrators may observe slowness after a server restart. The slowness will increase as the number of users to fetch will grow. After the first delay, subsequent fetch calls will be faster.

The observed behavior is intended, as Liferay clears the database cache after a server restart.
One approach to handle the issue is through a cache "warm-up" mechanism. To elaborate more, upon restarting the server:
1. Setup a crawler or jmeter script that runs the concerned query / visits the page where the datatable portlet is present so the query runs.
2. Once the server is restarted and while the traffic is not routed to the server (e.g.: the load balancer does not send any traffic yet), run the script to visit the pages directly on the node.
3. Enable traffic routing to the server.
Please note, the above method is untested and only provided as a hint. As it pertains to the domain of customizations, the ability of Liferay Support to assist with it is limited.