I'm currently developing an (android) app which should access and update data stored in my FIWARE instance and also respond to subscriptions.
Is there a recommended architecture on how I should access the data? Should I directly use the Orion NGSIv2 API or should I implement a middleware layer between my app and FIWARE?
According to NGSIv2 API specification:
FIWARE-NGSI v2 is intended to manage the entire lifecycle of context information, including updates, queries, registrations, and subscriptions.
By your short description in the question, you apparently just want to manage data (access and update: GET and UPDATE). So, you will not need any midleware to this.
Here, you can see how to use FIWARE Orion. This paper contains an example of architecture, collecting data at Android and sending to Orion. Another example of Orion usage. I think these are the first steps for you.
