diff --git a/retrieval/helpers_test.go b/retrieval/helpers_test.go
index 4961a968dd..05aadb3ea4 100644
--- a/retrieval/helpers_test.go
+++ b/retrieval/helpers_test.go
@@ -27,16 +27,16 @@ func (a nopAppendable) Appender() (storage.Appender, error) {
 
 type nopAppender struct{}
 
-func (a nopAppender) Add(labels.Labels, int64, float64) (string, error) { return "", nil }
-func (a nopAppender) AddFast(string, int64, float64) error              { return nil }
-func (a nopAppender) Commit() error                                     { return nil }
-func (a nopAppender) Rollback() error                                   { return nil }
+func (a nopAppender) Add(labels.Labels, int64, float64) (string, error)   { return "", nil }
+func (a nopAppender) AddFast(labels.Labels, string, int64, float64) error { return nil }
+func (a nopAppender) Commit() error                                       { return nil }
+func (a nopAppender) Rollback() error                                     { return nil }
 
 type collectResultAppender struct {
 	result []sample
 }
 
-func (a *collectResultAppender) AddFast(ref string, t int64, v float64) error {
+func (a *collectResultAppender) AddFast(m labels.Labels, ref string, t int64, v float64) error {
 	// Not implemented.
 	return storage.ErrNotFound
 }
diff --git a/retrieval/scrape.go b/retrieval/scrape.go
index 73873e98c6..ebfc3b4c02 100644
--- a/retrieval/scrape.go
+++ b/retrieval/scrape.go
@@ -751,8 +751,10 @@ loop:
 		}
 
 		ref, ok := sl.cache.getRef(yoloString(met))
+		var lset labels.Labels
+		p.Metric(&lset)
 		if ok {
-			switch err = app.AddFast(ref, t, v); err {
+			switch err = app.AddFast(lset, ref, t, v); err {
 			case nil:
 				if tp == nil {
 					e := sl.cache.lsets[ref]
@@ -945,10 +947,12 @@ func (sl *scrapeLoop) addReportSample(app storage.Appender, s string, t int64, v
 	// Suffix s with the invalid \xff unicode rune to avoid collisions
 	// with scraped metrics.
 	s2 := s + "\xff"
-
+	met := labels.Labels{
+		labels.Label{Name: labels.MetricName, Value: s},
+	}
 	ref, ok := sl.cache.getRef(s2)
 	if ok {
-		err := app.AddFast(ref, t, v)
+		err := app.AddFast(met, ref, t, v)
 		switch err {
 		case nil:
 			return nil
@@ -962,9 +966,7 @@ func (sl *scrapeLoop) addReportSample(app storage.Appender, s string, t int64, v
 			return err
 		}
 	}
-	met := labels.Labels{
-		labels.Label{Name: labels.MetricName, Value: s},
-	}
+
 	ref, err := app.Add(met, t, v)
 	switch err {
 	case nil:
diff --git a/retrieval/scrape_test.go b/retrieval/scrape_test.go
index 7ef8f6a818..5b4e23b554 100644
--- a/retrieval/scrape_test.go
+++ b/retrieval/scrape_test.go
@@ -885,8 +885,8 @@ func (app *errorAppender) Add(lset labels.Labels, t int64, v float64) (string, e
 	}
 }
 
-func (app *errorAppender) AddFast(ref string, t int64, v float64) error {
-	return app.collectResultAppender.AddFast(ref, t, v)
+func (app *errorAppender) AddFast(lset labels.Labels, ref string, t int64, v float64) error {
+	return app.collectResultAppender.AddFast(lset, ref, t, v)
 }
 
 func TestScrapeLoopAppendGracefullyIfAmendOrOutOfOrderOrOutOfBounds(t *testing.T) {
diff --git a/retrieval/target.go b/retrieval/target.go
index 2949074a65..f4f1e4609d 100644
--- a/retrieval/target.go
+++ b/retrieval/target.go
@@ -212,14 +212,14 @@ func (app *limitAppender) Add(lset labels.Labels, t int64, v float64) (string, e
 	return ref, nil
 }
 
-func (app *limitAppender) AddFast(ref string, t int64, v float64) error {
+func (app *limitAppender) AddFast(lset labels.Labels, ref string, t int64, v float64) error {
 	if !value.IsStaleNaN(v) {
 		app.i++
 		if app.i > app.limit {
 			return errSampleLimit
 		}
 	}
-	if err := app.Appender.AddFast(ref, t, v); err != nil {
+	if err := app.Appender.AddFast(lset, ref, t, v); err != nil {
 		return err
 	}
 	return nil
@@ -243,11 +243,11 @@ func (app *timeLimitAppender) Add(lset labels.Labels, t int64, v float64) (strin
 	return ref, nil
 }
 
-func (app *timeLimitAppender) AddFast(ref string, t int64, v float64) error {
+func (app *timeLimitAppender) AddFast(lset labels.Labels, ref string, t int64, v float64) error {
 	if t > app.maxTime {
 		return storage.ErrOutOfBounds
 	}
-	if err := app.Appender.AddFast(ref, t, v); err != nil {
+	if err := app.Appender.AddFast(lset, ref, t, v); err != nil {
 		return err
 	}
 	return nil
diff --git a/storage/fanout.go b/storage/fanout.go
index 56e6980739..9572f96d46 100644
--- a/storage/fanout.go
+++ b/storage/fanout.go
@@ -87,9 +87,13 @@ func (f *fanoutAppender) Add(l labels.Labels, t int64, v float64) (string, error
 	return "", nil
 }
 
-func (f *fanoutAppender) AddFast(ref string, t int64, v float64) error {
-	// TODO this is a cheat, and causes us to fall back to slow path even for local writes.
-	return ErrNotFound
+func (f *fanoutAppender) AddFast(l labels.Labels, ref string, t int64, v float64) error {
+	for _, appender := range f.appenders {
+		if err := appender.AddFast(l, ref, t, v); err != nil {
+			return err
+		}
+	}
+	return nil
 }
 
 func (f *fanoutAppender) Commit() error {
diff --git a/storage/interface.go b/storage/interface.go
index a1b5221a28..cb07728673 100644
--- a/storage/interface.go
+++ b/storage/interface.go
@@ -56,7 +56,7 @@ type Querier interface {
 type Appender interface {
 	Add(l labels.Labels, t int64, v float64) (string, error)
 
-	AddFast(ref string, t int64, v float64) error
+	AddFast(l labels.Labels, ref string, t int64, v float64) error
 
 	// Commit submits the collected samples and purges the batch.
 	Commit() error
diff --git a/storage/remote/write.go b/storage/remote/write.go
index f69561bc74..087ef8ca49 100644
--- a/storage/remote/write.go
+++ b/storage/remote/write.go
@@ -44,8 +44,9 @@ func labelsToMetric(ls labels.Labels) model.Metric {
 	return metric
 }
 
-func (*Storage) AddFast(ref string, t int64, v float64) error {
-	return storage.ErrNotFound
+func (s *Storage) AddFast(l labels.Labels, _ string, t int64, v float64) error {
+	_, err := s.Add(l, t, v)
+	return err
 }
 
 func (*Storage) Commit() error {
diff --git a/storage/tsdb/tsdb.go b/storage/tsdb/tsdb.go
index 09021fc5c0..63c4d52190 100644
--- a/storage/tsdb/tsdb.go
+++ b/storage/tsdb/tsdb.go
@@ -135,7 +135,7 @@ func (a appender) Add(lset labels.Labels, t int64, v float64) (string, error) {
 	return ref, err
 }
 
-func (a appender) AddFast(ref string, t int64, v float64) error {
+func (a appender) AddFast(_ labels.Labels, ref string, t int64, v float64) error {
 	err := a.a.AddFast(ref, t, v)
 
 	switch errors.Cause(err) {