db.mycoll.createIndex({a:1}, {expireAfterSeconds:100});

db.runCommand({insert:"mycoll", documents:[{a: new Date()}]});
{
  n: 1,
  electionId: ObjectId("7fffffff0000000000000002"),
  opTime: { ts: Timestamp({ t: 1697567560, i: 1 }), t: Long("2") },
  ok: 1,
  '$clusterTime': {
    clusterTime: Timestamp({ t: 1697567560, i: 1 }),
    signature: {
      hash: Binary(Buffer.from("171844c93c4de1a44f50a4ff32d591bfb90f1428", "hex"), 0),
      keyId: Long("7290770490346438661")
    }
  },
  operationTime: Timestamp({ t: 1697567560, i: 1 })
}

// Wait a few minutes …

// mongosh’s find() command returns nothing:
db.mycoll.find({}, null, {readConcern:{level:"snapshot", atClusterTime: Timestamp({ t: 1697567560, i: 2 })}});

// … but the server’s `find` command returns the expired document:
db.runCommand({find: "mycoll", readConcern:{level:"snapshot", atClusterTime: Timestamp({ t: 1697567560, i: 1 })}});
{
  cursor: {
    firstBatch: [
      {
        _id: ObjectId("652ed34800e1939439b41b7d"),
        a: ISODate("2023-10-17T18:32:40.160Z")
      }
    ],
    id: Long("0"),
    ns: 'test.mycoll',
    atClusterTime: Timestamp({ t: 1697567560, i: 1 })
  },
  ok: 1,
  '$clusterTime': {
    clusterTime: Timestamp({ t: 1697567800, i: 1 }),
    signature: {
      hash: Binary(Buffer.from("3bfdb41c158047adf591122381b46aa9e8c2e406", "hex"), 0),
      keyId: Long("7290770490346438661")
    }
  },
  operationTime: Timestamp({ t: 1697567800, i: 1 })
}