An Already Exists error is returned on operations which violate an at-most-once or uniqueness constraint. For example, an Already Exists error will be returned if:
  • Create Order is called with an already-used ref_id
  • Create Profile is called with an already-existing profile nickname
  • Accept Quote is called on a quote which has already been accepted
An Already Exists error has the following “meta” fields:
  • existing: The existing record which is the subject of the conflict (for example, the existing order with the same ref_id)
An Already Exists error may be benign if the client is retrying an earlier attempted operation which the client believes may have failed. However, if the request is not a retry, then resolving the error requires changing the request to avoid the conflict. 
{
  "detail": "nickname already exists",
  "meta": {
    "existing": {
      "id": "b7b77d82-e6a7-4ae9-9904-36231aedf985",
      "nickname": "existing nickname"
    }
  },
  "status": 409,
  "title": "Already Exists",
  "type": "https://developer.paxos.com/docs/v2/problems/already-exists"
}