By default solr comes with some caches that can help performance quite a bit, but they are not enabled in collective.solr's solrconfig.xml. Updating it to use the default settings from upstream (i.e. from https://github.com/apache/lucene-solr/blob/branch_8_11/solr/example/files/conf/solrconfig.xml#L356) should help performance with few downsides. (In our project, they improved search performance by 3-4 times and only added a few megabytes to RAM use.)
By default solr comes with some caches that can help performance quite a bit, but they are not enabled in collective.solr's solrconfig.xml. Updating it to use the default settings from upstream (i.e. from https://github.com/apache/lucene-solr/blob/branch_8_11/solr/example/files/conf/solrconfig.xml#L356) should help performance with few downsides. (In our project, they improved search performance by 3-4 times and only added a few megabytes to RAM use.)