COAP API suggestion
COAP API is like REST but over UDP.
It seems really appealing for a P2P application like Duniter. It is designed to handle millions of nodes.
- There are a lot of implementation, for Python, Java, NodeJS... : http://coap.technology/impls.html
- There are HTTP to COAP proxies existing : https://github.com/ibm-security-innovation/crosscoap which could be useful for testing before going on a full implementation.