{
  "topology_description": {
    "type": "ReplicaSetNoPrimary",
    "servers": [
      {
        "address": "a:27017",
        "type": "Unknown"
      },
      {
        "address": "b:27017",
        "type": "Unknown"
      }
    ]
  },
  "read_preference": {
    "mode": "Nearest",
    "maxStalenessSeconds": 90
  },
  "suitable_servers": [],
  "in_latency_window": []
}