diff --git a/services/meta/client.go b/services/meta/client.go
index 0ddf966e502..8dad1d6732a 100644
--- a/services/meta/client.go
+++ b/services/meta/client.go
@@ -694,11 +694,19 @@ func (c *Client) DropShard(id uint64) error {
 
 // CreateShardGroup creates a shard group on a database and policy for a given timestamp.
 func (c *Client) CreateShardGroup(database, policy string, timestamp time.Time) (*ShardGroupInfo, error) {
+	// Check under a read-lock
+	c.mu.RLock()
+	if sg, _ := c.cacheData.ShardGroupByTimestamp(database, policy, timestamp); sg != nil {
+		c.mu.RUnlock()
+		return sg, nil
+	}
+	c.mu.RUnlock()
+
 	c.mu.Lock()
 	defer c.mu.Unlock()
 
+	// Check again under the write lock
 	data := c.cacheData.Clone()
-
 	if sg, _ := data.ShardGroupByTimestamp(database, policy, timestamp); sg != nil {
 		return sg, nil
 	}
diff --git a/tsdb/engine/tsm1/encoding.go b/tsdb/engine/tsm1/encoding.go
index 798f163a041..4ad345545ea 100644
--- a/tsdb/engine/tsm1/encoding.go
+++ b/tsdb/engine/tsm1/encoding.go
@@ -111,26 +111,45 @@ func (a Values) Merge(b Values) Values {
 		return a
 	}
 
-	var i, j int
-	for ; i < len(a) && j < len(b); i++ {
-		av, bv := a[i].UnixNano(), b[j].UnixNano()
+	for i := 0; i < len(a) && len(b) > 0; i++ {
+		av, bv := a[i].UnixNano(), b[0].UnixNano()
+		// Value in a is greater than B, we need to merge
 		if av > bv {
-			a[i], b[j] = b[j], a[i]
+			// Save value in a
+			temp := a[i]
+
+			// Overwrite a with b
+			a[i] = b[0]
+
+			// Slide all values of b down 1
+			copy(b, b[1:])
+			b = b[:len(b)-1]
+
+			// See where value we save from a should be inserted in b to keep b sorted
+			k := sort.Search(len(b), func(i int) bool { return b[i].UnixNano() >= temp.UnixNano() })
+
+			if k == len(b) {
+				// Last position?
+				b = append(b, temp)
+			} else if b[k].UnixNano() != temp.UnixNano() {
+				// Save the last element, since it will get overwritten
+				last := b[len(b)-1]
+				// Somewhere in the middle of b, insert it only if it's not a duplicate
+				copy(b[k+1:], b[k:])
+				// Add the last vale to the end
+				b = append(b, last)
+				b[k] = temp
+			}
 		} else if av == bv {
-			a[i] = b[j]
-			j++
+			// Value in a an b are the same, use b
+			a[i] = b[0]
+			b = b[1:]
 		}
 	}
 
-	sort.Sort(b[j:])
-
-	if i >= len(a) {
-		if j+1 < len(b) && b[j].UnixNano() == b[j+1].UnixNano() {
-			j++
-		}
-		return append(a, b[j:]...)
+	if len(b) > 0 {
+		return append(a, b...)
 	}
-
 	return a
 }
 
@@ -442,24 +461,45 @@ func (a FloatValues) Merge(b FloatValues) FloatValues {
 		return a
 	}
 
-	var i, j int
-	for ; i < len(a) && j < len(b); i++ {
-		av, bv := a[i].UnixNano(), b[j].UnixNano()
+	for i := 0; i < len(a) && len(b) > 0; i++ {
+		av, bv := a[i].UnixNano(), b[0].UnixNano()
+		// Value in a is greater than B, we need to merge
 		if av > bv {
-			a[i], b[j] = b[j], a[i]
+			// Save value in a
+			temp := a[i]
+
+			// Overwrite a with b
+			a[i] = b[0]
+
+			// Slide all values of b down 1
+			copy(b, b[1:])
+			b = b[:len(b)-1]
+
+			// See where value we save from a should be inserted in b to keep b sorted
+			k := sort.Search(len(b), func(i int) bool { return b[i].UnixNano() >= temp.UnixNano() })
+
+			if k == len(b) {
+				// Last position?
+				b = append(b, temp)
+			} else if b[k].UnixNano() != temp.UnixNano() {
+				// Save the last element, since it will get overwritten
+				last := b[len(b)-1]
+				// Somewhere in the middle of b, insert it only if it's not a duplicate
+				copy(b[k+1:], b[k:])
+				// Add the last vale to the end
+				b = append(b, last)
+				b[k] = temp
+			}
 		} else if av == bv {
-			a[i] = b[j]
-			j++
+			// Value in a an b are the same, use b
+			a[i] = b[0]
+			b = b[1:]
 		}
 	}
 
-	if i >= len(a) {
-		if j+1 < len(b) && b[j].UnixNano() == b[j+1].UnixNano() {
-			j++
-		}
-		return append(a, b[j:]...)
+	if len(b) > 0 {
+		return append(a, b...)
 	}
-
 	return a
 }
 
@@ -655,24 +695,45 @@ func (a BooleanValues) Merge(b BooleanValues) BooleanValues {
 		return a
 	}
 
-	var i, j int
-	for ; i < len(a) && j < len(b); i++ {
-		av, bv := a[i].UnixNano(), b[j].UnixNano()
+	for i := 0; i < len(a) && len(b) > 0; i++ {
+		av, bv := a[i].UnixNano(), b[0].UnixNano()
+		// Value in a is greater than B, we need to merge
 		if av > bv {
-			a[i], b[j] = b[j], a[i]
+			// Save value in a
+			temp := a[i]
+
+			// Overwrite a with b
+			a[i] = b[0]
+
+			// Slide all values of b down 1
+			copy(b, b[1:])
+			b = b[:len(b)-1]
+
+			// See where value we save from a should be inserted in b to keep b sorted
+			k := sort.Search(len(b), func(i int) bool { return b[i].UnixNano() >= temp.UnixNano() })
+
+			if k == len(b) {
+				// Last position?
+				b = append(b, temp)
+			} else if b[k].UnixNano() != temp.UnixNano() {
+				// Save the last element, since it will get overwritten
+				last := b[len(b)-1]
+				// Somewhere in the middle of b, insert it only if it's not a duplicate
+				copy(b[k+1:], b[k:])
+				// Add the last vale to the end
+				b = append(b, last)
+				b[k] = temp
+			}
 		} else if av == bv {
-			a[i] = b[j]
-			j++
+			// Value in a an b are the same, use b
+			a[i] = b[0]
+			b = b[1:]
 		}
 	}
 
-	if i >= len(a) {
-		if j+1 < len(b) && b[j].UnixNano() == b[j+1].UnixNano() {
-			j++
-		}
-		return append(a, b[j:]...)
+	if len(b) > 0 {
+		return append(a, b...)
 	}
-
 	return a
 }
 
@@ -828,24 +889,45 @@ func (a IntegerValues) Merge(b IntegerValues) IntegerValues {
 		return a
 	}
 
-	var i, j int
-	for ; i < len(a) && j < len(b); i++ {
-		av, bv := a[i].UnixNano(), b[j].UnixNano()
+	for i := 0; i < len(a) && len(b) > 0; i++ {
+		av, bv := a[i].UnixNano(), b[0].UnixNano()
+		// Value in a is greater than B, we need to merge
 		if av > bv {
-			a[i], b[j] = b[j], a[i]
+			// Save value in a
+			temp := a[i]
+
+			// Overwrite a with b
+			a[i] = b[0]
+
+			// Slide all values of b down 1
+			copy(b, b[1:])
+			b = b[:len(b)-1]
+
+			// See where value we save from a should be inserted in b to keep b sorted
+			k := sort.Search(len(b), func(i int) bool { return b[i].UnixNano() >= temp.UnixNano() })
+
+			if k == len(b) {
+				// Last position?
+				b = append(b, temp)
+			} else if b[k].UnixNano() != temp.UnixNano() {
+				// Save the last element, since it will get overwritten
+				last := b[len(b)-1]
+				// Somewhere in the middle of b, insert it only if it's not a duplicate
+				copy(b[k+1:], b[k:])
+				// Add the last vale to the end
+				b = append(b, last)
+				b[k] = temp
+			}
 		} else if av == bv {
-			a[i] = b[j]
-			j++
+			// Value in a an b are the same, use b
+			a[i] = b[0]
+			b = b[1:]
 		}
 	}
 
-	if i >= len(a) {
-		if j+1 < len(b) && b[j].UnixNano() == b[j+1].UnixNano() {
-			j++
-		}
-		return append(a, b[j:]...)
+	if len(b) > 0 {
+		return append(a, b...)
 	}
-
 	return a
 }
 
@@ -1003,24 +1085,45 @@ func (a StringValues) Merge(b StringValues) StringValues {
 		return a
 	}
 
-	var i, j int
-	for ; i < len(a) && j < len(b); i++ {
-		av, bv := a[i].UnixNano(), b[j].UnixNano()
+	for i := 0; i < len(a) && len(b) > 0; i++ {
+		av, bv := a[i].UnixNano(), b[0].UnixNano()
+		// Value in a is greater than B, we need to merge
 		if av > bv {
-			a[i], b[j] = b[j], a[i]
+			// Save value in a
+			temp := a[i]
+
+			// Overwrite a with b
+			a[i] = b[0]
+
+			// Slide all values of b down 1
+			copy(b, b[1:])
+			b = b[:len(b)-1]
+
+			// See where value we save from a should be inserted in b to keep b sorted
+			k := sort.Search(len(b), func(i int) bool { return b[i].UnixNano() >= temp.UnixNano() })
+
+			if k == len(b) {
+				// Last position?
+				b = append(b, temp)
+			} else if b[k].UnixNano() != temp.UnixNano() {
+				// Save the last element, since it will get overwritten
+				last := b[len(b)-1]
+				// Somewhere in the middle of b, insert it only if it's not a duplicate
+				copy(b[k+1:], b[k:])
+				// Add the last vale to the end
+				b = append(b, last)
+				b[k] = temp
+			}
 		} else if av == bv {
-			a[i] = b[j]
-			j++
+			// Value in a an b are the same, use b
+			a[i] = b[0]
+			b = b[1:]
 		}
 	}
 
-	if i >= len(a) {
-		if j+1 < len(b) && b[j].UnixNano() == b[j+1].UnixNano() {
-			j++
-		}
-		return append(a, b[j:]...)
+	if len(b) > 0 {
+		return append(a, b...)
 	}
-
 	return a
 }
 
diff --git a/tsdb/engine/tsm1/encoding_test.go b/tsdb/engine/tsm1/encoding_test.go
index fbe01280357..3c63b9bf59a 100644
--- a/tsdb/engine/tsm1/encoding_test.go
+++ b/tsdb/engine/tsm1/encoding_test.go
@@ -386,6 +386,70 @@ func TestValues_MergeFloat(t *testing.T) {
 				tsm1.NewValue(1462498658288956853, 1.1),
 			},
 		},
+		{
+			a: []tsm1.Value{
+				tsm1.NewValue(4, 4.0),
+				tsm1.NewValue(5, 5.0),
+				tsm1.NewValue(6, 6.0),
+			},
+			b: []tsm1.Value{
+				tsm1.NewValue(1, 1.0),
+				tsm1.NewValue(2, 2.0),
+				tsm1.NewValue(3, 3.0),
+			},
+			exp: []tsm1.Value{
+				tsm1.NewValue(1, 1.0),
+				tsm1.NewValue(2, 2.0),
+				tsm1.NewValue(3, 3.0),
+				tsm1.NewValue(4, 4.0),
+				tsm1.NewValue(5, 5.0),
+				tsm1.NewValue(6, 6.0),
+			},
+		},
+		{
+			a: []tsm1.Value{
+				tsm1.NewValue(5, 5.0),
+				tsm1.NewValue(6, 6.0),
+			},
+			b: []tsm1.Value{
+				tsm1.NewValue(1, 1.0),
+				tsm1.NewValue(2, 2.0),
+				tsm1.NewValue(3, 3.0),
+				tsm1.NewValue(4, 4.0),
+				tsm1.NewValue(7, 7.0),
+				tsm1.NewValue(8, 8.0),
+			},
+			exp: []tsm1.Value{
+				tsm1.NewValue(1, 1.0),
+				tsm1.NewValue(2, 2.0),
+				tsm1.NewValue(3, 3.0),
+				tsm1.NewValue(4, 4.0),
+				tsm1.NewValue(5, 5.0),
+				tsm1.NewValue(6, 6.0),
+				tsm1.NewValue(7, 7.0),
+				tsm1.NewValue(8, 8.0),
+			},
+		},
+		{
+			a: []tsm1.Value{
+				tsm1.NewValue(1, 1.0),
+				tsm1.NewValue(2, 2.0),
+				tsm1.NewValue(3, 3.0),
+			},
+			b: []tsm1.Value{
+				tsm1.NewValue(4, 4.0),
+				tsm1.NewValue(5, 5.0),
+				tsm1.NewValue(6, 6.0),
+			},
+			exp: []tsm1.Value{
+				tsm1.NewValue(1, 1.0),
+				tsm1.NewValue(2, 2.0),
+				tsm1.NewValue(3, 3.0),
+				tsm1.NewValue(4, 4.0),
+				tsm1.NewValue(5, 5.0),
+				tsm1.NewValue(6, 6.0),
+			},
+		},
 	}
 
 	for i, test := range tests {
@@ -1226,3 +1290,20 @@ func BenchmarkValues_Deduplicate(b *testing.B) {
 		tsm1.Values(values).Deduplicate()
 	}
 }
+
+func BenchmarkValues_Merge(b *testing.B) {
+	valueCount := 1000
+	times := getTimes(valueCount, 60, time.Second)
+	a := make([]tsm1.Value, len(times))
+	c := make([]tsm1.Value, len(times))
+
+	for i, t := range times {
+		a[i] = tsm1.NewValue(t, float64(i))
+		c[i] = tsm1.NewValue(t+1, float64(i))
+	}
+
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		tsm1.Values(a).Merge(c)
+	}
+}