diff --git a/Makefile b/Makefile
index 590eb0f91..eb89acc59 100644
--- a/Makefile
+++ b/Makefile
@@ -53,7 +53,7 @@ documentation: search_index
 	godoc -http=:6060 -index -index_files='search_index'
 
 format:
-	find . -iname '*.go' | egrep -v "generated|\.(l|y)\.go" | xargs -n1 $(GOFMT) -w -s=true
+	find . -iname '*.go' | egrep -v "^./build/|generated|\.(l|y)\.go" | xargs -n1 $(GOFMT) -w -s=true
 
 model: dependencies preparation
 	$(MAKE) -C model
diff --git a/Makefile.INCLUDE b/Makefile.INCLUDE
index b8e253afd..db73a729b 100644
--- a/Makefile.INCLUDE
+++ b/Makefile.INCLUDE
@@ -38,7 +38,7 @@ GOCC		= $(GOROOT)/bin/go
 TMPDIR		= /tmp
 GOENV		= TMPDIR=$(TMPDIR) GOROOT=$(GOROOT) GOPATH=$(GOPATH)
 GO		= $(GOENV) $(GOCC)
-GOFMT		= $(GOENV) $(GOROOT)/bin/gofmt
+GOFMT		= $(GOROOT)/bin/gofmt
 
 LEVELDB_VERSION := 1.9.0
 PROTOCOL_BUFFERS_VERSION := 2.5.0
diff --git a/storage/metric/memory.go b/storage/metric/memory.go
index 1a4af813d..252d1ac60 100644
--- a/storage/metric/memory.go
+++ b/storage/metric/memory.go
@@ -141,6 +141,10 @@ func (s *stream) getRangeValues(in model.Interval) model.Values {
 	return result
 }
 
+func (s *stream) empty() bool {
+	return len(s.values) == 0
+}
+
 func newStream(metric model.Metric) *stream {
 	return &stream{
 		metric: metric,
@@ -175,14 +179,28 @@ func (s *memorySeriesStorage) AppendSample(sample model.Sample) error {
 	s.Lock()
 	defer s.Unlock()
 
-	metric := sample.Metric
-	fingerprint := model.NewFingerprintFromMetric(metric)
-	series, ok := s.fingerprintToSeries[*fingerprint]
+	fingerprint := model.NewFingerprintFromMetric(sample.Metric)
+	series := s.getOrCreateSeries(sample.Metric, fingerprint)
+	series.add(sample.Timestamp, sample.Value)
 
 	if s.wmCache != nil {
 		s.wmCache.Set(fingerprint, &Watermarks{High: sample.Timestamp})
 	}
 
+	return nil
+}
+
+func (s *memorySeriesStorage) CreateEmptySeries(metric model.Metric) {
+	s.Lock()
+	defer s.Unlock()
+
+	fingerprint := model.NewFingerprintFromMetric(metric)
+	s.getOrCreateSeries(metric, fingerprint)
+}
+
+func (s *memorySeriesStorage) getOrCreateSeries(metric model.Metric, fingerprint *model.Fingerprint) *stream {
+	series, ok := s.fingerprintToSeries[*fingerprint]
+
 	if !ok {
 		series = newStream(metric)
 		s.fingerprintToSeries[*fingerprint] = series
@@ -201,10 +219,71 @@ func (s *memorySeriesStorage) AppendSample(sample model.Sample) error {
 			s.labelNameToFingerprints[k] = labelNameValues
 		}
 	}
+	return series
+}
 
-	series.add(sample.Timestamp, sample.Value)
+func (s *memorySeriesStorage) Flush(flushOlderThan time.Time, queue chan<- model.Samples) {
+	emptySeries := []model.Fingerprint{}
 
-	return nil
+	s.RLock()
+	for fingerprint, stream := range s.fingerprintToSeries {
+		finder := func(i int) bool {
+			return stream.values[i].Timestamp.After(flushOlderThan)
+		}
+
+		stream.Lock()
+
+		i := sort.Search(len(stream.values), finder)
+		toArchive := stream.values[:i]
+		toKeep := stream.values[i:]
+		queued := make(model.Samples, 0, len(toArchive))
+
+		for _, value := range toArchive {
+			queued = append(queued, model.Sample{
+				Metric:    stream.metric,
+				Timestamp: value.Timestamp,
+				Value:     value.Value,
+			})
+		}
+
+		// BUG(all): this can deadlock if the queue is full, as we only ever clear
+		// the queue after calling this method:
+		// https://github.com/prometheus/prometheus/issues/275
+		queue <- queued
+
+		stream.values = toKeep
+
+		if len(toKeep) == 0 {
+			emptySeries = append(emptySeries, fingerprint)
+		}
+		stream.Unlock()
+	}
+	s.RUnlock()
+
+	s.Lock()
+	for _, fingerprint := range emptySeries {
+		if s.fingerprintToSeries[fingerprint].empty() {
+			s.dropSeries(&fingerprint)
+		}
+	}
+	s.Unlock()
+}
+
+// Drop all references to a series, including any samples.
+func (s *memorySeriesStorage) dropSeries(fingerprint *model.Fingerprint) {
+	series, ok := s.fingerprintToSeries[*fingerprint]
+	if !ok {
+		return
+	}
+	for k, v := range series.metric {
+		labelPair := model.LabelPair{
+			Name:  k,
+			Value: v,
+		}
+		delete(s.labelPairToFingerprints, labelPair)
+		delete(s.labelNameToFingerprints, k)
+	}
+	delete(s.fingerprintToSeries, *fingerprint)
 }
 
 // Append raw samples, bypassing indexing. Only used to add data to views,
diff --git a/storage/metric/tiered.go b/storage/metric/tiered.go
index bee4ce5f1..b352612cb 100644
--- a/storage/metric/tiered.go
+++ b/storage/metric/tiered.go
@@ -262,38 +262,10 @@ func (t *TieredStorage) Flush() {
 }
 
 func (t *TieredStorage) flushMemory(ttl time.Duration) {
-	t.memoryArena.RLock()
-	defer t.memoryArena.RUnlock()
-
-	cutOff := time.Now().Add(-1 * ttl)
+	flushOlderThan := time.Now().Add(-1 * ttl)
 
 	log.Println("Flushing...")
-
-	for _, stream := range t.memoryArena.fingerprintToSeries {
-		finder := func(i int) bool {
-			return stream.values[i].Timestamp.After(cutOff)
-		}
-
-		stream.Lock()
-
-		i := sort.Search(len(stream.values), finder)
-		toArchive := stream.values[:i]
-		toKeep := stream.values[i:]
-		queued := make(model.Samples, 0, len(toArchive))
-
-		for _, value := range toArchive {
-			queued = append(queued, model.Sample{
-				Metric:    stream.metric,
-				Timestamp: value.Timestamp,
-				Value:     value.Value,
-			})
-		}
-
-		t.appendToDiskQueue <- queued
-
-		stream.values = toKeep
-		stream.Unlock()
-	}
+	t.memoryArena.Flush(flushOlderThan, t.appendToDiskQueue)
 
 	queueLength := len(t.appendToDiskQueue)
 	if queueLength > 0 {
@@ -666,6 +638,7 @@ func (t *TieredStorage) GetMetricForFingerprint(f *model.Fingerprint) (model.Met
 	}
 	if m == nil {
 		m, err = t.DiskStorage.GetMetricForFingerprint(f)
+		t.memoryArena.CreateEmptySeries(m)
 	}
 	return m, err
 }