Is it possible to configure EPiFind to use multiple indexes?
I know this is possible with Elasticsearch - but I don't see ay obvious way in the docs.
I'm curious to know what's the use case for using a separate indexes? You can connect to additional indexes by configuring the IClient implementation in code:
IClient yourOtherIndexClient = new Client(serviceUrl, indexName);
Before you consider this it's worth reading the official documentation on performance of the Client class: http://world.episerver.com/documentation/Items/Developers-Guide/EPiServer-Find/10/DotNET-Client-API/Client-class/
It's worth bearing in mind that it could be more difficult to use separate indexes if you want to index CMS and Commerce content.