The ability to scale out SSRS, so that multiple report server instances can access a single report server database, is an Enterprise Edition-only feature. So when Ntirety’s Rodney Landrum was tasked with implementing a scale-out solution, with failover, for SSRS on SQL Server Standard Edition, it required some creative thinking. He wrote an article describing his solution, its merits and drawbacks.  The full article is available on Rodney’s blog.

https://www.simple-talk.com/sql/reporting-services/scaling-ssrs-sql-server-standard-edition/