Solr Stale Content server after content is updated

First off - please upgrade to Solr 8 and v8 of this module.

Solr itself does not index content immediately after it is informed of changed content, there is a brief delay in the changes being visible. As such, I'm not sure if this can ever be perfect, it might have to be documented as a known issue.

From the statement "The only way to get the new content is to clear all caches" this looks like an issue with the Drupal page or views cache rather than the Solr index cache, but yes, as Damien mentioned in the earlier comment, Solr does not index automatically, it will wait until a cron runs which is configured in Pantheon platform to run every hour.

To test if the stale content is related to the Solr index cache, after step 4 -> Unpublish one node that is rendered by the view, please run a manual re-index and if the stale content disappears, then this is related to the Solr index cache, but if not, then you must check the views page cache.

Changing the status of this issue to "Postponed" until the reporter try and test if the stale content is related to Solr cache or just a normal views page cache.