Don't forget hybrid solutions. I've done things in the past with: a) co-location for the main DB servers (allows you to be very specific about hardware choices

Don't forget hybrid solutions. I've done things in the past with: a) co-location for the main DB servers (allows you to be very specific about hardware choices: RAID cards and SSDs not just preferred manufacturer but also the exact model) and backup machines (needed higher density HDDs than could be supplied by hosting providers choice of dedicated servers) b) some unmanaged dedicated servers for the core servers that don't rely upon specific hardware requirements (HTTP servers, memcached, varnish). Also easier to slowly ramp up the number of these month on month. c) virtual boxes spun up when required to handle spikes in the load and then canned when it goes quieter again Even better if your hosting provider provides all 3 and can arrange a private VPN between the sets of hosts so you don't get billed for your 'internal' bandwidth.