5G presents a unique set of challenges for cellular network architecture. The architecture needs to be versatile in order to handle a variety of use cases. While network slicing has been proposed as a way to provide such versatility, it is also important to ensure that slices do not adversely interfere with each other. In other words, isolation among network slices is needed. Additionally, the large number of use cases also implies a large number of users, making it imperative that 5G architectures scale efficiently. In this paper we propose IsoRAN, which provides isolation and scaling along with the flexibility needed for 5G architecture. In IsoRAN, users are processed by daemon threads in the Cloud Radio Access Network (CRAN) architecture. Our design allows users from different use cases to be executed, in a distributed manner, on the most efficient hardware to ensure that the Service Level Agreements (SLAs) are met while minimising power consumption. Our experiments show that IsoRAN handles users with different SLA while providing isolation to reduce interference. This increased isolation reduces the drop rate for different users from 42% to nearly 0% in some cases. Finally, we run large scale simulations on real traces to show the benefits for power consumption and cost reduction scale while increasing the number of base stations.