I'm looking for three things really, and I know it's a bit of a "how long is a piece of string" question:
1) What is your experience of sizing and selecting and costing in advance of raising money (mainly AWS and EC2 - but any equivalent experience also welcome)
2) after having raised the funds how accurate was your prediction?
3) if you were raising again, what would you recommend doing instead?
Lastly, please speak about your experience as in, the number of users and concurrency you needed, on average how much space they required for each user, what db you were using.
I hope this is not asking too much!
It really comes down to your business model and assumptions. You tell me that your model says you will have 1000 users in Month 1, ramping up 100k users / month till month 12? I will then use that to plan everything else.
For one project we had a requirement of 500 concurrent users constantly using the system. Disk space was not as big a concern as memory/ram. To support these 500 users we needed about 6 large instances. Yes this is a lot of hardware for a very small # of connections which speaks to how intensive the app was.
If you need help be glad to take a look at your specific case.