I have been using Mongo for several years now on a fresh build that follows basically the outline you have here. The fresh build was triggered in part because o

I have been using Mongo for several years now on a fresh build that follows basically the outline you have here. The fresh build was triggered in part because of the cost (development time and infrastructure) in using Microsoft SQL Server. The only difference is that I got to step 5, realised I had two very different reporting requirements. One that Mongo works well with (real time aggregated data), and one which SQL works well with (high granularity, long time period, historical stuff). So, I use Mongo for the first requirement, and SQL for the later. I see many posts like this, and indeed many replies like it also (your thread currently). Curious, why do they always focus on have only one database to fit all their needs? Is my situation special, can't you just make a decision about what tool is best for the job and use it? Is there some eventuality where having databases specific to needs results in disaster that I am just not aware of?