They claim to support realtime indexing. I wonder what they really mean by that and how it impacts performance. SOLR is a great piece of software, I start using

They claim to support realtime indexing. I wonder what they really mean by that and how it impacts performance. SOLR is a great piece of software, I start using it 5 years ago and more recently implemented a near realtime indexing(publishing) integration but I always had to make some kind trade off between high performance and near "realtime indexing"