We typically do yearly performance audits with Percona to ensure our databases are optimally configured. We disable the query cache. We set innodb_buffer_pool_size based on a % of total memory (as MySQL will use more than that in total, much for allocating connection structs and things like that). We set innodb_flush_log_at_trx_commit to 0 which is not ideal for data integrity but gives us more performance. In practice, because of Google's Live Migration technology we have never experienced a crash due to hardware on our master nodes (LM will run an emergency migration for any server that has hardware that is detected to be going bad before it becomes a problem) and disks are abstracted away even further. Our main risk is the kernel crashing or MySQL crashing which we've been fortunate enough to not happen on our masters. Spanner provides ACID compliance by default with all the scaleability and performance we get out of it.