I have put down my thoughts in the architecture discussed in the blog. Although I have done substantial research to understand how things should work before deciding this architecture but I will be requiring huge amount of inputs from everyone to come to an architecture decision. Hardware entities which were thought while designing the entities are:
1. Master Web Server which will map different users to web servers placed in different geographical locations. (will prefer storing a mapping table in RAM)
2. Web Servers
3. Application Servers
4. Master Database Servers (to implement entity wise look up sharding)
5. Slave Database Servers.

Will really appreciate if some good inputs of using Cloud Computing are given and how to go about it against or in addition to the given architecture. Would like to in fact know people's view on when to decide using cloud computing techniques. Looking forward for inputs from the community.