allowDiskUse: true not working for serverless instance

I’m trying to this aggregation for a collection but getting memory limit error, then i used allowDiskUse: true . But it’s not working.

My aggreagation:

[
  {
    "$match": {
      "createdAt": {
        "$gte": ISODate("2024-05-15T14:42:55Z"),
        "$lte": ISODate("2024-07-15T14:42:55Z")
      }
    }
  },
  {
    "$group": {
      "_id": "$keyword",
      "count": { "$sum": 1 },
      "unique_ips": { "$addToSet": "$remoteHost" }
    }
  },
  {
    "$project": {
      "count": 1,
      "unique_ip_count": { "$size": "$unique_ips" }
    }
  },
  {
    "$sort": { "count": -1 }
  },
  {
    "$limit": 20
  }
]

Errror: 
 PlanExecutor error during aggregation :: caused by :: Exceeded memory limit for $group, but didn't allow external spilling; pass allowDiskUse:true to opt in, full

Hey thanks for the reply, but how can i run same aggregation without allowDiskUse option? Any workarounds? Thank you.