What is the best technology for federated search?

Question

Search engines

There is a task to make federated search.
https://en.wikipedia.org/wiki/Federated_search

But I can't find examples, libraries.
Maybe a similar search engine has a different name?
The idea is simple:
-- there are data sources (Full text engine, no-sql, relation databases, REST API, etc)
-- an inset request comes in (there will be a lot) - the service decides in which data source to update
-- a request comes to selex, the service translates the request into an accessible one for each service (DQL, SQL, REST, ect) and makes a request in parallel to each source, merges the data, sorts (according to some logic), translates it into a standard response format and returns it to the client.
Please tell me examples, architectures, technologies. I am sure that there are many similar services, but something with the search is not very ....

Answer 1

Its own Erlang tool :) it parallelizes well and makes queries anywhere and at once.