Check mongodb server information

Once you’re logged in to a mongodb server, you can check its information by invoking the hello command. You can just run db.hello() or db.runCommand({ hello: 1 })

The result below shows the details about the server, one of which indicating it’s the primary node.

db.hello()
{
  isWritablePrimary: true,
  topologyVersion: {
    processId: ObjectId('69ee092cc7c19099773b9870'),
    counter: Long('0')
  },
  maxBsonObjectSize: 16777216,
  maxMessageSizeBytes: 48000000,
  maxWriteBatchSize: 100000,
  localTime: ISODate('2026-04-26T13:19:28.582Z'),
  logicalSessionTimeoutMinutes: 30,
  connectionId: 5,
  minWireVersion: 0,
  maxWireVersion: 21,
  readOnly: false,
  ok: 1
}