diff --git a/pkg/aggregator/context_sketch_test.go b/pkg/aggregator/context_sketch_test.go
index d536791232ac..ebbbcec466c9 100644
--- a/pkg/aggregator/context_sketch_test.go
+++ b/pkg/aggregator/context_sketch_test.go
@@ -18,9 +18,9 @@ func TestContextSketchSampling(t *testing.T) {
 	resultSeries := ctxSketch.flush(12345.0)
 
 	expectedSketch := percentile.NewQSketch()
-	expectedSketch.Add(1)
-	expectedSketch.Add(5)
-	expectedSketch.Compress()
+	expectedSketch = expectedSketch.Add(1)
+	expectedSketch = expectedSketch.Add(5)
+	expectedSketch = expectedSketch.Compress()
 	expectedSeries := &percentile.SketchSeries{
 		ContextKey: contextKey,
 		Sketches:   []percentile.Sketch{{Timestamp: int64(12345), Sketch: expectedSketch}}}
@@ -57,15 +57,15 @@ func TestContextSketchSamplingMultiContexts(t *testing.T) {
 	sort.Sort(orderedSketchSeries)
 
 	expectedSketch1 := percentile.NewQSketch()
-	expectedSketch1.Add(1)
-	expectedSketch1.Add(3)
-	expectedSketch1.Compress()
+	expectedSketch1 = expectedSketch1.Add(1)
+	expectedSketch1 = expectedSketch1.Add(3)
+	expectedSketch1 = expectedSketch1.Compress()
 	expectedSeries1 := &percentile.SketchSeries{
 		ContextKey: contextKey1,
 		Sketches:   []percentile.Sketch{{Timestamp: int64(12345), Sketch: expectedSketch1}}}
 	expectedSketch2 := percentile.NewQSketch()
-	expectedSketch2.Add(1)
-	expectedSketch2.Compress()
+	expectedSketch2 = expectedSketch2.Add(1)
+	expectedSketch2 = expectedSketch2.Compress()
 	expectedSeries2 := &percentile.SketchSeries{
 		ContextKey: contextKey2,
 		Sketches:   []percentile.Sketch{{Timestamp: int64(12345), Sketch: expectedSketch2}}}
diff --git a/pkg/aggregator/dist_sampler_test.go b/pkg/aggregator/dist_sampler_test.go
index 126bcfd6cd3a..8cda66bae0da 100644
--- a/pkg/aggregator/dist_sampler_test.go
+++ b/pkg/aggregator/dist_sampler_test.go
@@ -95,9 +95,9 @@ func TestDistSamplerBucketSampling(t *testing.T) {
 	sketchSeries := distSampler.flush(10020.0)
 
 	expectedSketch := percentile.NewQSketch()
-	expectedSketch.Add(1)
-	expectedSketch.Add(2)
-	expectedSketch.Compress()
+	expectedSketch = expectedSketch.Add(1)
+	expectedSketch = expectedSketch.Add(2)
+	expectedSketch = expectedSketch.Compress()
 	expectedSeries := &percentile.SketchSeries{
 		Name:     "test.metric.name",
 		Tags:     []string{"a", "b"},
@@ -140,8 +140,8 @@ func TestDistSamplerContextSampling(t *testing.T) {
 	sketchSeries := orderedSketchSeries.sketchSeries
 
 	expectedSketch := percentile.NewQSketch()
-	expectedSketch.Add(1)
-	expectedSketch.Compress()
+	expectedSketch = expectedSketch.Add(1)
+	expectedSketch = expectedSketch.Compress()
 	expectedSeries1 := &percentile.SketchSeries{
 		Name:     "test.metric.name1",
 		Tags:     []string{"a", "b"},
diff --git a/pkg/aggregator/distribution.go b/pkg/aggregator/distribution.go
index bcae2612e621..d73a502ea5df 100644
--- a/pkg/aggregator/distribution.go
+++ b/pkg/aggregator/distribution.go
@@ -18,7 +18,7 @@ func NewDistribution() *Distribution {
 
 func (d *Distribution) addSample(sample *MetricSample, timestamp float64) {
 	// Insert sample value into the sketch
-	d.sketch.Add(sample.Value)
+	d.sketch = d.sketch.Add(sample.Value)
 	d.count++
 }
 
@@ -27,7 +27,7 @@ func (d *Distribution) flush(timestamp float64) (*percentile.SketchSeries, error
 		return &percentile.SketchSeries{}, percentile.NoSketchError{}
 	}
 	// compress the sketch before flushing
-	d.sketch.Compress()
+	d.sketch = d.sketch.Compress()
 	sketch := &percentile.SketchSeries{
 		Sketches: []percentile.Sketch{{Timestamp: int64(timestamp),
 			Sketch: d.sketch}},
diff --git a/pkg/aggregator/distribution_test.go b/pkg/aggregator/distribution_test.go
index a411271e99b6..d2d03ab15ff7 100644
--- a/pkg/aggregator/distribution_test.go
+++ b/pkg/aggregator/distribution_test.go
@@ -26,10 +26,10 @@ func TestDistributionSampling(t *testing.T) {
 	assert.Nil(t, err)
 
 	expectedSketch := percentile.NewQSketch()
-	expectedSketch.Add(1)
-	expectedSketch.Add(10)
-	expectedSketch.Add(5)
-	expectedSketch.Compress()
+	expectedSketch = expectedSketch.Add(1)
+	expectedSketch = expectedSketch.Add(10)
+	expectedSketch = expectedSketch.Add(5)
+	expectedSketch = expectedSketch.Compress()
 	expectedSeries := &percentile.SketchSeries{
 		Sketches: []percentile.Sketch{{Timestamp: int64(15), Sketch: expectedSketch}}}
 
diff --git a/pkg/aggregator/percentile/gk_array.go b/pkg/aggregator/percentile/gk_array.go
index 5659f4409bb7..477bef4d4ae6 100644
--- a/pkg/aggregator/percentile/gk_array.go
+++ b/pkg/aggregator/percentile/gk_array.go
@@ -89,7 +89,7 @@ func NewGKArray() GKArray {
 }
 
 // Add a new value to the summary.
-func (s *GKArray) Add(v float64) {
+func (s GKArray) Add(v float64) GKArray {
 	s.Count++
 	s.Sum += v
 	s.Avg += (v - s.Avg) / float64(s.Count)
@@ -101,12 +101,14 @@ func (s *GKArray) Add(v float64) {
 		s.Max = v
 	}
 	if s.Count%int(1/EPSILON) == 0 {
-		s.compress(nil)
+		return s.compress(nil)
 	}
+
+	return s
 }
 
 // Quantile returns an epsilon estimate of the element at quantile q.
-func (s *GKArray) Quantile(q float64) float64 {
+func (s GKArray) Quantile(q float64) float64 {
 	if q < 0 || q > 1 {
 		panic("Quantile out of bounds")
 	}
@@ -126,7 +128,7 @@ func (s *GKArray) Quantile(q float64) float64 {
 	}
 
 	if len(s.incoming) > 0 {
-		s.compress(nil)
+		s = s.compress(nil)
 	}
 
 	rank := int(q * float64(s.Count-1))
@@ -149,7 +151,7 @@ func (s *GKArray) Quantile(q float64) float64 {
 // interpolatedQuantile returns an estimate of the element at quantile q,
 // but interpolates between the lower and higher elements when Count is
 // less than 1/EPSILON
-func (s *GKArray) interpolatedQuantile(q float64) float64 {
+func (s GKArray) interpolatedQuantile(q float64) float64 {
 	rank := q * float64(s.Count-1)
 	indexBelow := int(rank)
 	indexAbove := indexBelow + 1
@@ -160,16 +162,16 @@ func (s *GKArray) interpolatedQuantile(q float64) float64 {
 	weightBelow := 1.0 - weightAbove
 
 	if len(s.incoming) > 0 {
-		s.compress(nil)
+		s = s.compress(nil)
 	}
 	// When Count is less than 1/EPSILON, all the entries will have G = 1, Delta = 0.
 	return weightBelow*s.Entries[indexBelow].V + weightAbove*s.Entries[indexAbove].V
 }
 
 // Merge another GKArray into this in-place.
-func (s *GKArray) Merge(o GKArray) {
+func (s GKArray) Merge(o GKArray) GKArray {
 	if o.Count == 0 {
-		return
+		return s
 	}
 	if s.Count == 0 {
 		s.Entries = o.Entries
@@ -179,9 +181,9 @@ func (s *GKArray) Merge(o GKArray) {
 		s.Max = o.Max
 		s.Sum = o.Sum
 		s.Avg = o.Avg
-		return
+		return s
 	}
-	o.compress(nil)
+	o = o.compress(nil)
 	spread := int(EPSILON * float64(o.Count-1))
 
 	/*
@@ -224,18 +226,18 @@ func (s *GKArray) Merge(o GKArray) {
 	if o.Max > s.Max {
 		s.Max = o.Max
 	}
-	s.compress(incomingEntries)
+	return s.compress(incomingEntries)
 }
 
 // Compress merges the incoming buffer into entries and compresses it.
-func (s *GKArray) Compress() {
+func (s GKArray) Compress() GKArray {
 	if len(s.incoming) == 0 {
-		return
+		return s
 	}
-	s.compress(nil)
+	return s.compress(nil)
 }
 
-func (s *GKArray) compress(incomingEntries Entries) {
+func (s GKArray) compress(incomingEntries Entries) GKArray {
 
 	// TODO[Charles]: use s.incoming and incomingEntries directly instead of merging them prior to compressing
 	for _, v := range s.incoming {
@@ -290,7 +292,7 @@ func (s *GKArray) compress(incomingEntries Entries) {
 			j++
 		}
 	}
-
 	s.Entries = merged
 	s.incoming = make([]float64, 0, int(1/EPSILON))
+	return s
 }
diff --git a/pkg/aggregator/percentile/gk_array_test.go b/pkg/aggregator/percentile/gk_array_test.go
index ade9ae9ac4f7..a5f6cd77f889 100644
--- a/pkg/aggregator/percentile/gk_array_test.go
+++ b/pkg/aggregator/percentile/gk_array_test.go
@@ -89,7 +89,7 @@ func EvaluateSketch(t *testing.T, n int, gen Generator) {
 	d := NewDataset()
 	for i := 0; i < n; i++ {
 		value := gen.Generate()
-		s.Add(value)
+		s = s.Add(value)
 		d.Add(value)
 	}
 	eps := float64(1.0e-6)
@@ -116,7 +116,7 @@ func TestConstant(t *testing.T) {
 		d := NewDataset()
 		for i := 0; i < n; i++ {
 			value := constantGenerator.Generate()
-			s.Add(value)
+			s = s.Add(value)
 			d.Add(value)
 		}
 		for _, q := range testQuantiles {
@@ -162,25 +162,25 @@ func TestMerge(t *testing.T) {
 		generator1 := NewNormal(35, 1)
 		for i := 0; i < n; i += 3 {
 			value := generator1.Generate()
-			s1.Add(value)
+			s1 = s1.Add(value)
 			d.Add(value)
 		}
 		s2 := NewGKArray()
 		generator2 := NewNormal(50, 2)
 		for i := 1; i < n; i += 3 {
 			value := generator2.Generate()
-			s2.Add(value)
+			s2 = s2.Add(value)
 			d.Add(value)
 		}
-		s1.Merge(s2)
+		s1 = s1.Merge(s2)
 		s3 := NewGKArray()
 		generator3 := NewNormal(40, 0.5)
 		for i := 2; i < n; i += 3 {
 			value := generator3.Generate()
-			s3.Add(value)
+			s3 = s3.Add(value)
 			d.Add(value)
 		}
-		s1.Merge(s3)
+		s1 = s1.Merge(s3)
 
 		eps := float64(1e-6)
 		for _, q := range testQuantiles {
@@ -199,7 +199,7 @@ func TestInterpolatedQuantile(t *testing.T) {
 		if n < int(1/EPSILON) {
 			s := NewGKArray()
 			for i := 0; i < n; i++ {
-				s.Add(float64(i))
+				s = s.Add(float64(i))
 			}
 			for _, q := range testQuantiles {
 				expected := q * (float64(n) - 1)
diff --git a/pkg/aggregator/percentile/sketch_series.go b/pkg/aggregator/percentile/sketch_series.go
index 140f19ee36dc..f0e077bc5845 100644
--- a/pkg/aggregator/percentile/sketch_series.go
+++ b/pkg/aggregator/percentile/sketch_series.go
@@ -36,6 +36,16 @@ func NewQSketch() QSketch {
 	return QSketch{NewGKArray()}
 }
 
+// Add a value to the qsketch
+func (q QSketch) Add(v float64) QSketch {
+	return QSketch{GKArray: q.GKArray.Add(v)}
+}
+
+// Compress the qsketch
+func (q QSketch) Compress() QSketch {
+	return QSketch{GKArray: q.GKArray.Compress()}
+}
+
 // NoSketchError is the error returned when not enough samples have been
 //submitted to generate a sketch
 type NoSketchError struct{}
@@ -79,7 +89,6 @@ func unmarshalSketches(summarySketches []agentpayload.SketchPayload_Summary_Sket
 			})
 	}
 	return sketches
-
 }
 
 // MarshalSketchSeries serializes sketch series using protocol buffers