[Answer]-Bad Request: Unknown identifier id

It sounds like there’s a mismatch between the user table schema in cassandra and your User model. What version of cassandra and cqlengine are you using? Could you jump into cqlsh, describe the keyspace the user table is in, and post the output?

Also, I don’t know if this is just a test app, but inserting a User row with an id provided by the client is a serious security problem. I could easily take control of another user’s account by simply hitting your register_user route with another user’s id. You should also be hashing the password, not storing it in plain text.