Even though Jira already provides a rich REST API, there is a number of reasons why Query Feed may be a better choice.
Streamlined data model
Query Feed for Jira has been built to make access to Jira issue data as easy as possible.
It includes only the information you configured (based on a query and field selection).
All data is available at a single URL.
The data is in a format that is very easy to consume. It does not require you to understand complex field metadata and use to interpret Jira issues. All the information is directly available in a flat JSON map, matching field names with values.
See Configuration in Query Feed for more information.
Available anywhere with simple security model
With Query Feed for Jira, the data can be easily consumed from any source - but it is still secure!
It does not require any authentication (login/password or OAuth) or setup procedures, except for an access token which is part of the feed URL.
Query Feed data is always served over HTTPS, protecting the access token and data from interception.
The data can be immediately and easily downloaded from any source. It may be consumed by a batch process or even a lightweight script. It may even be used directly from a serverless web application thanks to cross-origin resource sharing.
Only selected fields from issues matching feed query are exposed.
Query Feed cannot be used to make any modifications in Jira. At the same time there is an easy way to prevent access to feed data by invalidating the access token.
See Security in Query Feed for more information.