Essentially, we are developing using Ruby on Rails and want to make a highly scalable ticketing system. Essentially we will have a small database (containing event details and tickets sold) that will spike with large numbers of reads (users visiting the site, up to 1-2 million per day) and a low-ish level of writes (write when a user requests a ticket, and when they buy it).
The writes need to persisted to disk, but we are keen on keeping the whole database in memory (perhaps using memcached). Right now we are going to build this on Mysql (activerecord on RoR).
Question is, will this setup be scalable for our future needs where we may need to organize dozens of events with 10s of millions of hits.