{
  "heartbeatFrequencyMS": 120000,
  "topology_description": {
    "type": "ReplicaSetWithPrimary",
    "servers": [
      {
        "address": "a:27017",
        "type": "RSPrimary",
        "avg_rtt_ms": 5,
        "lastUpdateTime": 0,
        "maxWireVersion": 6,
        "lastWrite": {
          "lastWriteDate": {
            "$numberLong": "1"
          }
        }
      },
      {
        "address": "b:27017",
        "type": "RSSecondary",
        "avg_rtt_ms": 50,
        "lastUpdateTime": 0,
        "maxWireVersion": 6,
        "lastWrite": {
          "lastWriteDate": {
            "$numberLong": "1"
          }
        }
      }
    ]
  },
  "read_preference": {
    "mode": "Nearest",
    "maxStalenessSeconds": 130
  },
  "suitable_servers": [
    {
      "address": "a:27017",
      "type": "RSPrimary",
      "avg_rtt_ms": 5,
      "lastUpdateTime": 0,
      "maxWireVersion": 6,
      "lastWrite": {
        "lastWriteDate": {
          "$numberLong": "1"
        }
      }
    },
    {
      "address": "b:27017",
      "type": "RSSecondary",
      "avg_rtt_ms": 50,
      "lastUpdateTime": 0,
      "maxWireVersion": 6,
      "lastWrite": {
        "lastWriteDate": {
          "$numberLong": "1"
        }
      }
    }
  ],
  "in_latency_window": [
    {
      "address": "a:27017",
      "type": "RSPrimary",
      "avg_rtt_ms": 5,
      "lastUpdateTime": 0,
      "maxWireVersion": 6,
      "lastWrite": {
        "lastWriteDate": {
          "$numberLong": "1"
        }
      }
    }
  ]
}