38531095.scala

case class PendingResult(k1: Long, k2: String, futureResults: ResultSetFuture)

val pendingResults = ArrayBuffer.empty[PendingResult]
for (i <- 1 to iterations) {
  val k1 = ...
  val k2 = ...
  val futureResults = session.executeAsync(s"SELECT * FROM ${tableName} WHERE k1=${k1} AND k2='${k2}'")
  pendingResults += PendingResult(k1, k2, futureResults)
}

for (pendingResult <- pendingResults) {
  val results = pendingResult.futureResults.get()
  val ids = ArrayBuffer.empty[Long]
  for (row <- results) {
    ids += row.getLong("id")
  }
  if (verbose) {
    println(s"${pendingResult.k1}, ${pendingResult.k2}, ${ids.mkString(",")}")
  }
}