Sure, we have clusters that run at performance rating of 95% on categories and 97% on products, as you have so many sites this would mak sense, full database redundancy, load balanced. Usually Amazon AWS based (although any cloud or bare metal works), with the option of either redundancy install for established sites or Google ranking install for new sites, Google treats the architecture differently.
Currently with a reference Magento site Google ranked 9,400pages out of the 15,000product database across four country stores, in a few weeks, the performance and ranking of the clusters is better than the enterprise companies have themselves such as Saks, Sephora, and as such the sites auto rank themselves.
We just placed a 15,000product Wordpress/Woocommerce site on the cluster and tested the results, one active web server was 83% performance on category page, three active web servers 93% performance, and three active web servers with varnish enabled was 97%, the product page was 99% performance, no one in the world has this.
We were speaking about it today, we truly have absolutely no idea why people do not understand that with such technology, the need for backlinks, content writing, marketing becomes optional rather than mandatory, with the holiday season approaching where 70% of all yearly sales are made, single web servers or even small clusters are just not going to make the grade. Instead of being behind the top enterprise retailers, we pushed the technology above their level to out rank them, quicker, if only Adobe had our architecture for their enterprise clients, but they don't 
