Compared with "classical" web, multi-tier applications, mobile applications have common and specific requirements concerning data persistence and processing. In mobile apps, database features can be distinctly analyzed for the client (minimalistic, isolated, memory-only) and the server (data rich, centralized, distributed, synchronized and disk-based) layers. Currently, a few lite relational database products reign the persistence for client platforms of mobile applications. There are two main objectives of this paper. First is to investigate storage options for major mobile platforms. Second is to point out some major differences between SQL and NoSQL datastores in terms of deployment, data model, schema design, data definition and manipulation. As NoSQL movement lacks standardization,... from NoSQL products family MongoDB was chosen as reference, due to its strengths and popularity among developers. PostgreSQL serves the position of SQL DBMSs representative due to its popularity and conformity with SQL standards.