diff --git a/bitmap.go b/bitmap.go
index 55664b24b..d30a9192a 100644
--- a/bitmap.go
+++ b/bitmap.go
@@ -16,6 +16,8 @@ type Bitmap struct {
 
 	// Attributes associated with the bitmap.
 	Attrs map[string]interface{}
+
+	cacheoveride uint64
 }
 
 // NewBitmap returns a new instance of Bitmap.
@@ -174,6 +176,26 @@ func (b *Bitmap) InvalidateCount() {
 	}
 }
 
+//increment the bitmap cached counter, note this is an optimization that assumes that the caller is aware the size increased
+func (b *Bitmap) IncrementCount(i uint64) {
+	seg := b.segment(i / SliceWidth)
+	if seg != nil {
+		seg.n++
+	}
+}
+func (b *Bitmap) DecrementCount(i uint64) {
+	seg := b.segment(i / SliceWidth)
+	if seg != nil {
+		if seg.n > 0 {
+			seg.n--
+		}
+	}
+}
+func (b *Bitmap) SetCount(i uint64, count uint64) {
+	seg := b.segment(i / SliceWidth)
+	seg.n = count
+}
+
 // Count returns the number of set bits in the bitmap.
 func (b *Bitmap) Count() uint64 {
 	var n uint64
@@ -312,7 +334,6 @@ func (s *BitmapSegment) Difference(other *BitmapSegment) *BitmapSegment {
 // SetBit sets the i-th bit of the bitmap.
 func (s *BitmapSegment) SetBit(i uint64) (changed bool) {
 	s.ensureWritable()
-
 	changed, _ = s.data.Add(i)
 	if changed {
 		s.n++
diff --git a/cache.go b/cache.go
index 8eab72368..4345c93fd 100644
--- a/cache.go
+++ b/cache.go
@@ -5,6 +5,7 @@ import (
 	"fmt"
 	"io"
 	"sort"
+	"sync"
 	"time"
 
 	"github.com/golang/groupcache/lru"
@@ -97,6 +98,7 @@ var _ Cache = &LRUCache{}
 
 // RankCache represents a cache with sorted entries.
 type RankCache struct {
+	mu       sync.Mutex
 	entries  map[uint64]uint64
 	rankings []BitmapPair // cached, ordered list
 
@@ -117,6 +119,8 @@ func NewRankCache() *RankCache {
 
 // Add adds a bitmap to the cache.
 func (c *RankCache) Add(bitmapID uint64, n uint64) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
 	// Ignore if the bit count on the bitmap is below the threshold.
 	if n < c.ThresholdValue {
 		return
@@ -124,19 +128,13 @@ func (c *RankCache) Add(bitmapID uint64, n uint64) {
 
 	c.entries[bitmapID] = n
 
-	c.Invalidate()
-	// If size is larger than the threshold then trim it.
-	if len(c.entries) > c.ThresholdLength {
-		for id, n := range c.entries {
-			if n <= c.ThresholdValue {
-				delete(c.entries, id)
-			}
-		}
-	}
+	c.invalidate()
 }
 
 // BulkAdd adds a bitmap to the cache unsorted. You should Invalidate after completion.
 func (c *RankCache) BulkAdd(bitmapID uint64, n uint64) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
 	if n < c.ThresholdValue {
 		return
 	}
@@ -145,13 +143,23 @@ func (c *RankCache) BulkAdd(bitmapID uint64, n uint64) {
 }
 
 // Get returns a bitmap with a given id.
-func (c *RankCache) Get(bitmapID uint64) uint64 { return c.entries[bitmapID] }
+func (c *RankCache) Get(bitmapID uint64) uint64 {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	return c.entries[bitmapID]
+}
 
 // Len returns the number of items in the cache.
-func (c *RankCache) Len() int { return len(c.entries) }
+func (c *RankCache) Len() int {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	return len(c.entries)
+}
 
 // BitmapIDs returns a list of all bitmap IDs in the cache.
 func (c *RankCache) BitmapIDs() []uint64 {
+	c.mu.Lock()
+	defer c.mu.Unlock()
 	a := make([]uint64, 0, len(c.entries))
 	for id := range c.entries {
 		a = append(a, id)
@@ -162,6 +170,15 @@ func (c *RankCache) BitmapIDs() []uint64 {
 
 // update reorders the entries by rank.
 func (c *RankCache) Invalidate() {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	c.invalidate()
+
+}
+func (c *RankCache) invalidate() {
+	if time.Now().Sub(c.updateTime).Seconds() < 10 {
+		return
+	}
 	//fmt.Println("RankCache Update")
 	// Convert cache to a sorted list.
 	rankings := make([]BitmapPair, 0, len(c.entries))
@@ -183,6 +200,14 @@ func (c *RankCache) Invalidate() {
 
 	// Reset counters.
 	c.updateTime, c.updateN = time.Now(), 0
+	// If size is larger than the threshold then trim it.
+	if len(c.entries) > c.ThresholdLength {
+		for id, n := range c.entries {
+			if n <= c.ThresholdValue {
+				delete(c.entries, id)
+			}
+		}
+	}
 }
 
 // Top returns an ordered list of bitmaps.
diff --git a/fragment.go b/fragment.go
index 493640ef0..5516e05ec 100644
--- a/fragment.go
+++ b/fragment.go
@@ -351,8 +351,10 @@ func (f *Fragment) bitmap(bitmapID uint64, updateCache bool) *Bitmap {
 			slice:    f.slice,
 			writable: false,
 		}},
+		cacheoveride: 0,
 	}
 	bm.InvalidateCount()
+	bm.cacheoveride = bm.Count()
 
 	if updateCache {
 		// Update cache.
@@ -380,6 +382,7 @@ func (f *Fragment) setBit(bitmapID, profileID uint64) (changed bool, bool error)
 	}
 
 	// Write to storage.
+
 	if changed, err = f.storage.Add(pos); err != nil {
 		return false, err
 	}
@@ -399,8 +402,13 @@ func (f *Fragment) setBit(bitmapID, profileID uint64) (changed bool, bool error)
 
 	// Update the cache.
 	bm := f.bitmap(bitmapID, true)
-	bm.SetBit(profileID)
-	bm.InvalidateCount() //maybe a perf opportunity?
+	if bm.cacheoveride > 0 {
+		bm.SetCount(profileID, bm.cacheoveride)
+		bm.cacheoveride = 0
+	} else {
+		bm.IncrementCount(profileID)
+	}
+
 	f.cache.Add(bitmapID, bm.Count())
 
 	f.stats.Count("setN", 1)
@@ -443,9 +451,13 @@ func (f *Fragment) clearBit(bitmapID, profileID uint64) (bool, error) {
 	}
 
 	// Update the cache.
-	bm := f.bitmap(bitmapID, true)
-	bm.ClearBit(profileID)
-	bm.InvalidateCount() //maybe a perf opportunity?
+	bm := f.bitmap(bitmapID, false)
+	if bm.cacheoveride > 0 {
+		bm.SetCount(profileID, bm.cacheoveride)
+		bm.cacheoveride = 0
+	} else {
+		bm.DecrementCount(profileID)
+	}
 	f.cache.Add(bitmapID, bm.Count())
 
 	f.stats.Count("clearN", 1)