scalable multi-tier architecture as web service

Hello, we are seeking for a reliable partner for a fast growing iterative software project who solves the following task: A scalable multi-tier architecture based on: Presentation tier: RESTful Webservice (.net) Logic tier: .net Data tier: .net connected to an MSSQL Database cluster The complete system should run on windows server system. First attempt is to develop a prototype for a small subset of interface methods and database tables. Important for us is that the software architecture can hold the speed of further dynamically growing (amount of users/servers) and development (interface methods / database views and tables). Do not hesitate to ask detailed questions.