Vespa has been around for a LONG time. When I worked at Yahoo back in 2005-2007 the Flickr team were using it to scale Flickr - they were integrating it in order to serve things like public tag pages, to take the load off their MySQL cluster.
I remember understanding it as the internal equivalent to something like Solr, although actually it predated it - looks like the first public Solr open source release (coming out of CNET) was January 2006.
Yeah, I worked with the Flickr team on that project. Scaling to billions of photos, with partial update support of popularity for ranking.
Back then, the properties had to stand up their own Vespa cluster(s), later on we created a managed service out of it. And, yes, the original plan for Vespa was to be a Vertical Search Platform, that is where the name Vespa comes from. More on the history in this blog post https://blog.vespa.ai/vespa-is-becoming-its-own-company/
I remember understanding it as the internal equivalent to something like Solr, although actually it predated it - looks like the first public Solr open source release (coming out of CNET) was January 2006.