Operating in the humanitarian sector of South Sudan comes with an endless number of challenges. High personnel turnover makes it difficult to maintain servers, and VSAT-only connectivity results in dial-up performance for both city and field locations. Despite this, there is a great need to communicate detailed GIS data beyond what can be printed on paper. To fill in this gap, REACH Initiative has been developing platforms that use mobile- & offline-first technologies to address these issues. This talk will focus on a specific platform REACH has been developing to allow less technical users to make their own offline maps with minimal maintenance. This map CMS pulls data from a managed GraphQL service and generates progressive web apps using a static site generator with Mapbox GL templates. Emphasis will be placed on the big picture of how these pieces connect together. This specific example will be framed in a larger discussion of how to best develop complex software for low-bandwidth environments. During over two year's worth of development in the field, it will tell the story of what different approaches were attempted, and why these failed in the humanitarian context from a performance and maintenance perspective.