libmill | Go-style concurrency in C

Does Boost.Fiber automatically yield on network requests (if I understand correctly they yield the CPU during I/O), such as a database call over the network? I want to use it for setting up blocking database calls where I am inserting a lot of information and have a lot of small records that need to be inserted when they are received. My other choice would be libdill/libmill for the microthreading.

The general idea would be:

1. receive data
2. create fiber and pass it the data
3. fiber gets a database connection and sends the INSERT query (libpqxx with postgres)
4. other fibers run and can access the database while the database query is in flight
5. query returns from database, do error handling and process response

Do fibers work this way as I am envisioning it?

This is the simplified base structure for the code using RapidJSON and boost.fiber, but I'm getting the messages from the network (websocket):