[rogerbinns]

> However I always feared in the back of my head we would have to move off of it if our service got too big

I like to call that "nice problem to have" territory. There is nothing to fear from being too successful, or from having the problems of success. Success problems can be solved by the application of people, time and money. And like all optimization you measure first to make sure you really have the problems you think you do, Amdahl's law etc.

Far more likely you'll have the problems of not being successful, such as no attention or money from customers and investors. Or not being in the business you think you are in. There isn't really that much point putting in infrastructure just in case you get successful, if that same infrastructure takes time to develop, and slows development.

I'd be delighted having a service "too big" for MongoDB! After all it would mean being more successful than the companies listed at http://www.mongodb.org/display/DOCS/Production+Deployments