Vespa was actually very cool at the time as a document-oriented search engine, occupying the same niche as Solr and elaborations of that like ElasticSearch. But I don't know if it's competitive today. This blog post says it's "developed by Yahoo" which is I guess true. But it was originally an acquisition, largely developed by a team in Norway, and apparently most Vespa development still happens there.
very, it's outcompeting most vector databases on features and maturity when it comes to vector search while having very powerful and flexible and proven text search too
The tricky part is, it's more a platform to build complex search systems with then "just" a vector database. So if a found a company today which focus is to create clever multi phase search pipelines and train (e.g. domain adopt) LLMs for calculating embeddings etc. then it's probably _the_ best solution by far, you probably can get away with having only AI engines devops and a single programmer (who might also most times just do devops). But if you need to deeply integrate it into a different existing search system things are less grate.
And I would love to see some modernization, like having a format for structured queries which is more widely supported then YQL... (eying graphql here)