@knuthollund Here is a good guide I used: https://www.percona.com/blog/2014/01/28/10-mysql-performance-tuning-settings-after-installation/

From it:
query_cache_size: the query cache is a well known bottleneck that can be seen even when concurrency is moderate. The best option is to disable it from day 1 by setting query_cache_size = 0 (now the default on MySQL 5.6) and to use other ways to speed up read queries: good indexing, adding replicas to spread the read load or using an external cache (memcache or redis for instance).