curl --request GET \
  --url https://mango.sievedata.com/v2/user/concurrency \
  --header 'X-API-Key: <api-key>'

{
  "max_concurrency": 123,
  "num_current": 123,
  "num_processing": 123,
  "num_queued": 123,
  "num_limited": 123
}