diff --git a/follow-recommendations-service/common/src/main/scala/com/twitter/follow_recommendations/common/rankers/weighted_candidate_source_ranker/WeightedCandidateSourceRanker.scala b/follow-recommendations-service/common/src/main/scala/com/twitter/follow_recommendations/common/rankers/weighted_candidate_source_ranker/WeightedCandidateSourceRanker.scala
index c6f55adbc..58ef8d33a 100644
--- a/follow-recommendations-service/common/src/main/scala/com/twitter/follow_recommendations/common/rankers/weighted_candidate_source_ranker/WeightedCandidateSourceRanker.scala
+++ b/follow-recommendations-service/common/src/main/scala/com/twitter/follow_recommendations/common/rankers/weighted_candidate_source_ranker/WeightedCandidateSourceRanker.scala
@@ -1,4 +1,5 @@
 package com.twitter.follow_recommendations.common.rankers.weighted_candidate_source_ranker
+
 import com.twitter.follow_recommendations.common.base.Ranker
 import com.twitter.follow_recommendations.common.models.CandidateUser
 import com.twitter.follow_recommendations.common.rankers.common.DedupCandidates
@@ -19,65 +20,42 @@ import com.twitter.timelines.configapi.HasParams
  * @param shuffleFn the shuffle function that will be used to shuffle each algorithm's sorted candidate list.
  * @param dedup whether to remove duplicated candidates from the final output.
  */
-class WeightedCandidateSourceRanker[Target <: HasParams](
-  basedRanker: WeightedCandidateSourceBaseRanker[
-    CandidateSourceIdentifier,
-    CandidateUser
-  ],
-  shuffleFn: Seq[CandidateUser] => Seq[CandidateUser],
-  dedup: Boolean)
-    extends Ranker[Target, CandidateUser] {
 
-  val name: String = this.getClass.getSimpleName
+
+class WeightedCandidateSourceRanker(
+  basedRanker: WeightedCandidateSourceBaseRanker[CandidateSourceIdentifier, CandidateUser],
+  shuffleFn: Seq[CandidateUser] => Seq[CandidateUser],
+  dedup: Boolean
+) extends Ranker[Target, CandidateUser] {
 
   override def rank(target: Target, candidates: Seq[CandidateUser]): Stitch[Seq[CandidateUser]] = {
-    val scribeRankingInfo: Boolean =
-      target.params(WeightedCandidateSourceRankerParams.ScribeRankingInfoInWeightedRanker)
-    val rankedCands = rankCandidates(group(candidates))
-    Stitch.value(if (scribeRankingInfo) Utils.addRankingInfo(rankedCands, name) else rankedCands)
+    val scribeRankingInfo = target.params(WeightedCandidateSourceRankerParams.ScribeRankingInfoInWeightedRanker)
+    val rankedCandidates = rankCandidates(group(candidates))
+    Stitch.value(if (scribeRankingInfo) Utils.addRankingInfo(rankedCandidates, name) else rankedCandidates)
   }
 
-  private def group(
-    candidates: Seq[CandidateUser]
-  ): Map[CandidateSourceIdentifier, Seq[CandidateUser]] = {
-    val flattened = for {
-      candidate <- candidates
-      identifier <- candidate.getPrimaryCandidateSource
-    } yield (identifier, candidate)
-    flattened.groupBy(_._1).mapValues(_.map(_._2))
+  private def group(candidates: Seq[CandidateUser]): Map[CandidateSourceIdentifier, Seq[CandidateUser]] = {
+    candidates.flatMap(_.getPrimaryCandidateSource.map(identifier => (identifier, Seq(_)))).toMap
   }
 
-  private def rankCandidates(
-    input: Map[CandidateSourceIdentifier, Seq[CandidateUser]]
-  ): Seq[CandidateUser] = {
-    // Sort and shuffle candidates per candidate source.
-    // Note 1: Using map instead mapValue here since mapValue somehow caused infinite loop when used as part of Stream.
-    val sortAndShuffledCandidates = input.map {
-      case (source, candidates) =>
-        // Note 2: toList is required here since candidates is a view, and it will result in infinit loop when used as part of Stream.
-        // Note 3: there is no real sorting logic here, it assumes the input is already sorted by candidate sources
-        val sortedCandidates = candidates.toList
-        source -> shuffleFn(sortedCandidates).iterator
-    }
+  private def rankCandidates(input: Map[CandidateSourceIdentifier, Seq[CandidateUser]]): Seq[CandidateUser] = {
+    val sortAndShuffledCandidates = input.mapValues(shuffleFn compose (_.toList)).toSeq
     val rankedCandidates = basedRanker(sortAndShuffledCandidates)
-
     if (dedup) DedupCandidates(rankedCandidates) else rankedCandidates
   }
+
+  val name: String = getClass.getSimpleName
 }
 
 object WeightedCandidateSourceRanker {
-
-  def build[Target <: HasParams](
+  def build(
     candidateSourceWeight: Map[CandidateSourceIdentifier, Double],
     shuffleFn: Seq[CandidateUser] => Seq[CandidateUser] = identity,
     dedup: Boolean = false,
     randomSeed: Option[Long] = None
-  ): WeightedCandidateSourceRanker[Target] = {
+  ): WeightedCandidateSourceRanker = {
     new WeightedCandidateSourceRanker(
-      new WeightedCandidateSourceBaseRanker(
-        candidateSourceWeight,
-        WeightMethod.WeightedRandomSampling,
-        randomSeed = randomSeed),
+      new WeightedCandidateSourceBaseRanker(candidateSourceWeight, WeightMethod.WeightedRandomSampling, randomSeed),
       shuffleFn,
       dedup
     )
@@ -85,16 +63,11 @@ object WeightedCandidateSourceRanker {
 }
 
 object WeightedCandidateSourceRankerWithoutRandomSampling {
-  def build[Target <: HasParams](
-    candidateSourceWeight: Map[CandidateSourceIdentifier, Double]
-  ): WeightedCandidateSourceRanker[Target] = {
+  def build(candidateSourceWeight: Map[CandidateSourceIdentifier, Double]): WeightedCandidateSourceRanker = {
     new WeightedCandidateSourceRanker(
-      new WeightedCandidateSourceBaseRanker(
-        candidateSourceWeight,
-        WeightMethod.WeightedRoundRobin,
-        randomSeed = None),
+      new WeightedCandidateSourceBaseRanker(candidateSourceWeight, WeightMethod.WeightedRoundRobin, None),
       identity,
-      false,
+      false
     )
   }
 }