PostgreSQL vs MySQL benchmarks when a 2nd level cache is included Has anyone been able to find any benchmarks comparing PostgreSQL and MySQL performance when they are used by a system through Hibernate (or another comparable ORM) and the 2nd level cache (backed by Memcache, EhCache, etc) is enabled?  

I've seen a lot of benchmarks comparing and MySQL performance (most of which are outdated but that's besides the point) but none of them ever seem to factor in a 2nd level cache.  That makes the benchmark entirely irrelevant to me because any highly scalable system that relies on a relational database is going to need a 2nd level cache.

PS Let me know if this is not the site to ask this question and it belongs on one of the many other StackExchange sites instead.  Please migrate the question as usual if that's the case, thanks.
Left unconfigured, PostgreSQL will outperform MySQL. In fact, left unconfigured, InnoDB in some older versions of MySQL are better than newer versions of MySQL.

Tuning PostgreSQL and MySQL and then Benchmarking for occassional usage in the presence of memcached is a lot like building two cars, drag racing them, and then parking them forever. That only leaves the open road and whatever happens to be in the middle of highway.

If you have a large working set and high turn around of data, then perhaps memcached and other second-tier caches woiuld be unnecessary. From that point forward, choice of database and benchmarking would be worthwhile and intriguing.