Re structured data - in theory, yes :) We have to work a bit more in that direction. Here's the first step - querying table data, which could be really helpful for reports, financial data, etc. In regards to the storage backend - it's currently Elasticsearch, OpenSearch, SQL+FAISS/Milvus/Weaviate (when using dense vectors/dense passage retrieval). There is also an in-memory datastore using python primitives for fast prototyping.

(Also, latest features highlights here https://www.deepset.ai/blog/new-features-in-haystack-v1.0)