Oracle SES extended PeopleSoft search for several years but proved to be complicated to implement and with some limitations (indexing required frequently etc ...)
We are now waiting for Elasticsearch to be delivered in PeopleTools 8.56 and backported to 8.55.
To ease the deployment, Oracle has included a feature where you can switch to Elastic without stopping PeopleSoft.
You can configure several search sources with a priority. Once decommissioning SES, you will transparently switch to Elastic !