DigitalGov search (formerly USASearch) is an embeddable search engine that can be used to search federal websites. The Drupal 8 version like previous versions features:
Ability to index nodes by content type
Ability to specify specific nodes to be indexed
Ability to select view mode to show in search results
This version is a major rewrite. It uses the same principles, but the replacements are done using the JSONPath specification instead of JSON Pointer. That allows for more interesting features, like create N requests from a single subrequest if the replacement pattern returns an array of replacements.