Healthcare Information Systems are a big business. Currently there is an explosion of EHR/EMR products available on the market, and the best tools are really expensive. Many developing countries and healthcare providers cannot access such tools, and for those who can, there is not a clear strategy for the evolution, scaling, and cost of these electronic health products. The lack of standard-based implementations conduct to the creation of isolated information silos that cannot be exploited (i.e. shared between providers to promote a holistic view of each patient's medical history). This paper exposes the main elements behind a Standard-based Open Source EHR Platform that is future-proof and allows to evolve and scale with minimal cost. The proposed EHR Architecture is based on openEHR specifications, adding elements emerged from research and development experiences, leading to a design that can be implemented in any modern technology. Different implementations will be interoperable by design. This Platform will leverage contexts of scarce resources, reusing clinical knowledge, a common set of software components and services.