Don't even start with the Express version. We started with SQL Standard, then had memory / CPU constraints and moved to SQL Enterprise, being the easier upgrade path. Now pricing is ridiculous and web scale is limited, so we're looking to get out from under the cost/limitations of it. Unfortunately; we have a lot of development, years of it, around MSSQL at this point and migration is difficult. If I had to do it over, I'd find another solution, there are plenty, one that web scaled and was either open source or cost effective at web scale. MSSQL is not!