diff --git a/storage/local/crashrecovery.go b/storage/local/crashrecovery.go
index d52bdfcb08..cbb0061bf4 100644
--- a/storage/local/crashrecovery.go
+++ b/storage/local/crashrecovery.go
@@ -250,17 +250,28 @@ func (p *persistence) sanitizeSeries(
 		// consistent with the checkpoint, so we have to take a closer
 		// look.
 		if s.headChunkClosed {
-			// This is the easy case as we don't have any chunks in
-			// heads.db. Treat this series as a freshly unarchived
-			// one. No chunks or chunkDescs in memory, no current
-			// head chunk.
+			// This is the easy case as we have all chunks on
+			// disk. Treat this series as a freshly unarchived one
+			// by loading the chunkDescs and setting all parameters
+			// based on the loaded chunkDescs.
+			cds, err := p.loadChunkDescs(fp, clientmodel.Latest)
+			if err != nil {
+				log.Errorf(
+					"Failed to load chunk descriptors for metric %v, fingerprint %v: %s",
+					s.metric, fp, err,
+				)
+				purge()
+				return fp, false
+			}
 			log.Warnf(
 				"Treating recovered metric %v, fingerprint %v, as freshly unarchived, with %d chunks in series file.",
-				s.metric, fp, chunksInFile,
+				s.metric, fp, len(cds),
 			)
-			s.chunkDescs = nil
-			s.chunkDescsOffset = chunksInFile
-			s.persistWatermark = 0
+			s.chunkDescs = cds
+			s.chunkDescsOffset = 0
+			s.savedFirstTime = cds[0].firstTime()
+			s.lastTime = cds[len(cds)-1].lastTime()
+			s.persistWatermark = len(cds)
 			s.modTime = modTime
 			return fp, true
 		}
@@ -275,8 +286,8 @@ func (p *persistence) sanitizeSeries(
 		// First, throw away the chunkDescs without chunks.
 		s.chunkDescs = s.chunkDescs[s.persistWatermark:]
 		numMemChunkDescs.Sub(float64(s.persistWatermark))
-		// Load all the chunk descs (which assumes we have none from the future).
-		cds, err := p.loadChunkDescs(fp, clientmodel.Now())
+		// Load all the chunk descs.
+		cds, err := p.loadChunkDescs(fp, clientmodel.Latest)
 		if err != nil {
 			log.Errorf(
 				"Failed to load chunk descriptors for metric %v, fingerprint %v: %s",
@@ -287,6 +298,7 @@ func (p *persistence) sanitizeSeries(
 		}
 		s.persistWatermark = len(cds)
 		s.chunkDescsOffset = 0
+		s.savedFirstTime = cds[0].firstTime()
 		s.modTime = modTime
 
 		lastTime := cds[len(cds)-1].lastTime()
@@ -395,14 +407,11 @@ func (p *persistence) cleanUpArchiveIndexes(
 		if _, err := p.archivedFingerprintToMetrics.Delete(fp); err != nil {
 			return err
 		}
-		series := newMemorySeries(clientmodel.Metric(m), false, clientmodel.Earliest)
-		cds, err := p.loadChunkDescs(clientmodel.Fingerprint(fp), clientmodel.Now())
+		cds, err := p.loadChunkDescs(clientmodel.Fingerprint(fp), clientmodel.Latest)
 		if err != nil {
 			return err
 		}
-		series.chunkDescs = cds
-		series.chunkDescsOffset = 0
-		series.persistWatermark = len(cds)
+		series := newMemorySeries(clientmodel.Metric(m), cds, p.seriesFileModTime(clientmodel.Fingerprint(fp)))
 		fpToSeries[clientmodel.Fingerprint(fp)] = series
 		return nil
 	}); err != nil {
diff --git a/storage/local/delta.go b/storage/local/delta.go
index ebb92e3cda..ebff38f15b 100644
--- a/storage/local/delta.go
+++ b/storage/local/delta.go
@@ -94,9 +94,11 @@ func (c deltaEncodedChunk) add(s *metric.SamplePair) []chunk {
 	}
 
 	baseValue := c.baseValue()
-	// TODO(beorn7): Once https://github.com/prometheus/prometheus/issues/481 is
-	// fixed, we should panic here if dt is negative.
 	dt := s.Timestamp - c.baseTime()
+	if dt < 0 {
+		panic("time delta is less than zero")
+	}
+
 	dv := s.Value - baseValue
 	tb := c.timeBytes()
 	vb := c.valueBytes()
@@ -382,7 +384,7 @@ func (it *deltaEncodedChunkIterator) timestampAtIndex(idx int) clientmodel.Times
 		// Take absolute value for d8.
 		return clientmodel.Timestamp(binary.LittleEndian.Uint64(it.c[offset:]))
 	default:
-		panic("Invalid number of bytes for time delta")
+		panic("invalid number of bytes for time delta")
 	}
 }
 
@@ -407,7 +409,7 @@ func (it *deltaEncodedChunkIterator) sampleValueAtIndex(idx int) clientmodel.Sam
 			return it.baseV + clientmodel.SampleValue(int32(binary.LittleEndian.Uint32(it.c[offset:])))
 		// No d8 for ints.
 		default:
-			panic("Invalid number of bytes for integer delta")
+			panic("invalid number of bytes for integer delta")
 		}
 	} else {
 		switch it.vBytes {
@@ -417,7 +419,7 @@ func (it *deltaEncodedChunkIterator) sampleValueAtIndex(idx int) clientmodel.Sam
 			// Take absolute value for d8.
 			return clientmodel.SampleValue(math.Float64frombits(binary.LittleEndian.Uint64(it.c[offset:])))
 		default:
-			panic("Invalid number of bytes for floating point delta")
+			panic("invalid number of bytes for floating point delta")
 		}
 	}
 }
diff --git a/storage/local/doubledelta.go b/storage/local/doubledelta.go
index f11471aa52..7377ab2bd0 100644
--- a/storage/local/doubledelta.go
+++ b/storage/local/doubledelta.go
@@ -339,10 +339,7 @@ func (c doubleDeltaEncodedChunk) addFirstSample(s *metric.SamplePair) []chunk {
 func (c doubleDeltaEncodedChunk) addSecondSample(s *metric.SamplePair, tb, vb deltaBytes) []chunk {
 	baseTimeDelta := s.Timestamp - c.baseTime()
 	if baseTimeDelta < 0 {
-		// TODO(beorn7): We ignore this irregular case for now. Once
-		// https://github.com/prometheus/prometheus/issues/481 is
-		// fixed, we should panic here instead.
-		return []chunk{&c}
+		panic("base time delta is less than zero")
 	}
 	c = c[:doubleDeltaHeaderBytes]
 	if tb >= d8 || bytesNeededForUnsignedTimestampDelta(baseTimeDelta) >= d8 {
@@ -511,7 +508,7 @@ func (it *doubleDeltaEncodedChunkIterator) timestampAtIndex(idx int) clientmodel
 		// Take absolute value for d8.
 		return clientmodel.Timestamp(binary.LittleEndian.Uint64(it.c[offset:]))
 	default:
-		panic("Invalid number of bytes for time delta")
+		panic("invalid number of bytes for time delta")
 	}
 }
 
@@ -555,7 +552,7 @@ func (it *doubleDeltaEncodedChunkIterator) sampleValueAtIndex(idx int) clientmod
 				clientmodel.SampleValue(int32(binary.LittleEndian.Uint32(it.c[offset:])))
 		// No d8 for ints.
 		default:
-			panic("Invalid number of bytes for integer delta")
+			panic("invalid number of bytes for integer delta")
 		}
 	} else {
 		switch it.vBytes {
@@ -567,7 +564,7 @@ func (it *doubleDeltaEncodedChunkIterator) sampleValueAtIndex(idx int) clientmod
 			// Take absolute value for d8.
 			return clientmodel.SampleValue(math.Float64frombits(binary.LittleEndian.Uint64(it.c[offset:])))
 		default:
-			panic("Invalid number of bytes for floating point delta")
+			panic("invalid number of bytes for floating point delta")
 		}
 	}
 }
diff --git a/storage/local/index/leveldb.go b/storage/local/index/leveldb.go
index 4a1345ab3a..37630b8b3e 100644
--- a/storage/local/index/leveldb.go
+++ b/storage/local/index/leveldb.go
@@ -109,13 +109,18 @@ func (l *LevelDB) Delete(key encoding.BinaryMarshaler) (bool, error) {
 	if err != nil {
 		return false, err
 	}
-	err = l.storage.Delete(k, l.writeOpts)
+	// Note that Delete returns nil if k does not exist. So we have to test
+	// for existence with Get first.
+	_, err = l.storage.Get(k, l.readOpts)
 	if err == leveldb.ErrNotFound {
 		return false, nil
 	}
 	if err != nil {
 		return false, err
 	}
+	if err = l.storage.Delete(k, l.writeOpts); err != nil {
+		return false, err
+	}
 	return true, nil
 }
 
diff --git a/storage/local/persistence.go b/storage/local/persistence.go
index 2e7cdb0563..a629e23f43 100644
--- a/storage/local/persistence.go
+++ b/storage/local/persistence.go
@@ -643,7 +643,7 @@ func (p *persistence) checkpointSeriesMapAndHeads(fingerprintToSeries *seriesMap
 						return
 					}
 				} else {
-					// This is the non-persisted head chunk. Fully marshal it.
+					// This is a non-persisted chunk. Fully marshal it.
 					if err = w.WriteByte(byte(chunkDesc.c.encoding())); err != nil {
 						return
 					}
@@ -853,6 +853,7 @@ func (p *persistence) loadSeriesMapAndHeads() (sm *seriesMap, chunksToPersist in
 			modTime:          modTime,
 			chunkDescsOffset: int(chunkDescsOffset),
 			savedFirstTime:   clientmodel.Timestamp(savedFirstTime),
+			lastTime:         chunkDescs[len(chunkDescs)-1].lastTime(),
 			headChunkClosed:  persistWatermark >= numChunkDescs,
 		}
 	}
@@ -1173,38 +1174,27 @@ func (p *persistence) purgeArchivedMetric(fp clientmodel.Fingerprint) (err error
 
 // unarchiveMetric deletes an archived fingerprint and its metric, but (in
 // contrast to purgeArchivedMetric) does not un-index the metric.  If a metric
-// was actually deleted, the method returns true and the first time of the
-// deleted metric. The caller must have locked the fingerprint.
-func (p *persistence) unarchiveMetric(fp clientmodel.Fingerprint) (
-	deletedAnything bool,
-	firstDeletedTime clientmodel.Timestamp,
-	err error,
-) {
+// was actually deleted, the method returns true and the first time and last
+// time of the deleted metric. The caller must have locked the fingerprint.
+func (p *persistence) unarchiveMetric(fp clientmodel.Fingerprint) (deletedAnything bool, err error) {
 	defer func() {
 		if err != nil {
 			p.setDirty(true)
 		}
 	}()
 
-	firstTime, _, has, err := p.archivedFingerprintToTimeRange.Lookup(fp)
-	if err != nil || !has {
-		return false, firstTime, err
-	}
 	deleted, err := p.archivedFingerprintToMetrics.Delete(codable.Fingerprint(fp))
-	if err != nil {
-		return false, firstTime, err
-	}
-	if !deleted {
-		log.Errorf("Tried to delete non-archived fingerprint %s from archivedFingerprintToMetrics index. This should never happen.", fp)
+	if err != nil || !deleted {
+		return false, err
 	}
 	deleted, err = p.archivedFingerprintToTimeRange.Delete(codable.Fingerprint(fp))
 	if err != nil {
-		return false, firstTime, err
+		return false, err
 	}
 	if !deleted {
 		log.Errorf("Tried to delete non-archived fingerprint %s from archivedFingerprintToTimeRange index. This should never happen.", fp)
 	}
-	return true, firstTime, nil
+	return true, nil
 }
 
 // close flushes the indexing queue and other buffered data and releases any
diff --git a/storage/local/persistence_test.go b/storage/local/persistence_test.go
index 1954823a01..34bb672b39 100644
--- a/storage/local/persistence_test.go
+++ b/storage/local/persistence_test.go
@@ -17,6 +17,7 @@ import (
 	"reflect"
 	"sync"
 	"testing"
+	"time"
 
 	clientmodel "github.com/prometheus/client_golang/model"
 
@@ -354,11 +355,11 @@ func testCheckpointAndLoadSeriesMapAndHeads(t *testing.T, encoding chunkEncoding
 
 	fpLocker := newFingerprintLocker(10)
 	sm := newSeriesMap()
-	s1 := newMemorySeries(m1, true, 0)
-	s2 := newMemorySeries(m2, false, 0)
-	s3 := newMemorySeries(m3, false, 0)
-	s4 := newMemorySeries(m4, true, 0)
-	s5 := newMemorySeries(m5, true, 0)
+	s1 := newMemorySeries(m1, nil, time.Time{})
+	s2 := newMemorySeries(m2, nil, time.Time{})
+	s3 := newMemorySeries(m3, nil, time.Time{})
+	s4 := newMemorySeries(m4, nil, time.Time{})
+	s5 := newMemorySeries(m5, nil, time.Time{})
 	s1.add(&metric.SamplePair{Timestamp: 1, Value: 3.14})
 	s3.add(&metric.SamplePair{Timestamp: 2, Value: 2.7})
 	s3.headChunkClosed = true
@@ -416,8 +417,8 @@ func testCheckpointAndLoadSeriesMapAndHeads(t *testing.T, encoding chunkEncoding
 		if loadedS3.head().c != nil {
 			t.Error("head chunk not evicted")
 		}
-		if loadedS3.chunkDescsOffset != -1 {
-			t.Errorf("want chunkDescsOffset -1, got %d", loadedS3.chunkDescsOffset)
+		if loadedS3.chunkDescsOffset != 0 {
+			t.Errorf("want chunkDescsOffset 0, got %d", loadedS3.chunkDescsOffset)
 		}
 		if !loadedS3.headChunkClosed {
 			t.Error("headChunkClosed is false")
@@ -546,22 +547,19 @@ func testFingerprintsModifiedBefore(t *testing.T, encoding chunkEncoding) {
 		}
 	}
 
-	unarchived, firstTime, err := p.unarchiveMetric(1)
+	unarchived, err := p.unarchiveMetric(1)
 	if err != nil {
 		t.Fatal(err)
 	}
 	if !unarchived {
-		t.Fatal("expected actual unarchival")
+		t.Error("expected actual unarchival")
 	}
-	if firstTime != 2 {
-		t.Errorf("expected first time 2, got %v", firstTime)
-	}
-	unarchived, firstTime, err = p.unarchiveMetric(1)
+	unarchived, err = p.unarchiveMetric(1)
 	if err != nil {
 		t.Fatal(err)
 	}
 	if unarchived {
-		t.Fatal("expected no unarchival")
+		t.Error("expected no unarchival")
 	}
 
 	expectedFPs = map[clientmodel.Timestamp][]clientmodel.Fingerprint{
@@ -831,16 +829,13 @@ func testIndexing(t *testing.T, encoding chunkEncoding) {
 		verifyIndexedState(i, t, batches[i], indexedFpsToMetrics, p)
 		for fp, m := range b.fpToMetric {
 			p.unindexMetric(fp, m)
-			unarchived, firstTime, err := p.unarchiveMetric(fp)
+			unarchived, err := p.unarchiveMetric(fp)
 			if err != nil {
 				t.Fatal(err)
 			}
 			if !unarchived {
 				t.Errorf("%d. metric not unarchived", i)
 			}
-			if firstTime != 1 {
-				t.Errorf("%d. expected firstTime=1, got %v", i, firstTime)
-			}
 			delete(indexedFpsToMetrics, fp)
 		}
 	}
diff --git a/storage/local/series.go b/storage/local/series.go
index 60c428441f..07388a2e5f 100644
--- a/storage/local/series.go
+++ b/storage/local/series.go
@@ -162,6 +162,9 @@ type memorySeries struct {
 	// first chunk before its chunk desc is evicted. In doubt, this field is
 	// just set to the oldest possible timestamp.
 	savedFirstTime clientmodel.Timestamp
+	// The timestamp of the last sample in this series. Needed for fast access to
+	// ensure timestamp monotonicity during ingestion.
+	lastTime clientmodel.Timestamp
 	// Whether the current head chunk has already been finished.  If true,
 	// the current head chunk must not be modified anymore.
 	headChunkClosed bool
@@ -175,28 +178,29 @@ type memorySeries struct {
 }
 
 // newMemorySeries returns a pointer to a newly allocated memorySeries for the
-// given metric. reallyNew defines if the memorySeries is a genuinely new series
-// or (if false) a series for a metric being unarchived, i.e. a series that
-// existed before but has been evicted from memory. If reallyNew is false,
-// firstTime is ignored (and set to the lowest possible timestamp instead - it
-// will be set properly upon the first eviction of chunkDescs).
-func newMemorySeries(
-	m clientmodel.Metric,
-	reallyNew bool,
-	firstTime clientmodel.Timestamp,
-) *memorySeries {
-	if !reallyNew {
-		firstTime = clientmodel.Earliest
+// given metric. chunkDescs and modTime in the new series are set according to
+// the provided parameters. chunkDescs can be nil or empty if this is a
+// genuinely new time series (i.e. not one that is being unarchived). In that
+// case, headChunkClosed is set to false, and firstTime and lastTime are both
+// set to clientmodel.Earliest. The zero value for modTime can be used if the
+// modification time of the series file is unknown (e.g. if this is a genuinely
+// new series).
+func newMemorySeries(m clientmodel.Metric, chunkDescs []*chunkDesc, modTime time.Time) *memorySeries {
+	firstTime := clientmodel.Earliest
+	lastTime := clientmodel.Earliest
+	if len(chunkDescs) > 0 {
+		firstTime = chunkDescs[0].firstTime()
+		lastTime = chunkDescs[len(chunkDescs)-1].lastTime()
 	}
-	s := memorySeries{
-		metric:          m,
-		headChunkClosed: !reallyNew,
-		savedFirstTime:  firstTime,
+	return &memorySeries{
+		metric:           m,
+		chunkDescs:       chunkDescs,
+		headChunkClosed:  len(chunkDescs) > 0,
+		savedFirstTime:   firstTime,
+		lastTime:         lastTime,
+		persistWatermark: len(chunkDescs),
+		modTime:          modTime,
 	}
-	if !reallyNew {
-		s.chunkDescsOffset = -1
-	}
-	return &s
 }
 
 // add adds a sample pair to the series. It returns the number of newly
@@ -231,6 +235,8 @@ func (s *memorySeries) add(v *metric.SamplePair) int {
 	for _, c := range chunks[1:] {
 		s.chunkDescs = append(s.chunkDescs, newChunkDesc(c))
 	}
+
+	s.lastTime = v.Timestamp
 	return len(chunks) - 1
 }
 
@@ -243,7 +249,7 @@ func (s *memorySeries) maybeCloseHeadChunk() bool {
 	if s.headChunkClosed {
 		return false
 	}
-	if time.Now().Sub(s.head().lastTime().Time()) > headChunkTimeout {
+	if time.Now().Sub(s.lastTime.Time()) > headChunkTimeout {
 		s.headChunkClosed = true
 		// Since we cannot modify the head chunk from now on, we
 		// don't need to bother with cloning anymore.
diff --git a/storage/local/storage.go b/storage/local/storage.go
index 66b7aa961b..90e1de21a4 100644
--- a/storage/local/storage.go
+++ b/storage/local/storage.go
@@ -135,6 +135,7 @@ type memorySeriesStorage struct {
 	numSeries                   prometheus.Gauge
 	seriesOps                   *prometheus.CounterVec
 	ingestedSamplesCount        prometheus.Counter
+	outOfOrderSamplesCount      prometheus.Counter
 	invalidPreloadRequestsCount prometheus.Counter
 	maintainSeriesDuration      *prometheus.SummaryVec
 }
@@ -203,6 +204,12 @@ func NewMemorySeriesStorage(o *MemorySeriesStorageOptions) Storage {
 			Name:      "ingested_samples_total",
 			Help:      "The total number of samples ingested.",
 		}),
+		outOfOrderSamplesCount: prometheus.NewCounter(prometheus.CounterOpts{
+			Namespace: namespace,
+			Subsystem: subsystem,
+			Name:      "out_of_order_samples_total",
+			Help:      "The total number of samples that were discarded because their timestamps were at or before the last received sample for a series.",
+		}),
 		invalidPreloadRequestsCount: prometheus.NewCounter(prometheus.CounterOpts{
 			Namespace: namespace,
 			Subsystem: subsystem,
@@ -550,6 +557,13 @@ func (s *memorySeriesStorage) Append(sample *clientmodel.Sample) {
 		s.fpLocker.Lock(fp)
 	}
 	series := s.getOrCreateSeries(fp, sample.Metric)
+
+	if sample.Timestamp <= series.lastTime {
+		s.fpLocker.Unlock(fp)
+		log.Warnf("Ignoring sample with out-of-order timestamp for fingerprint %v (%v): %v is not after %v", fp, series.metric, sample.Timestamp, series.lastTime)
+		s.outOfOrderSamplesCount.Inc()
+		return
+	}
 	completedChunksCount := series.add(&metric.SamplePair{
 		Value:     sample.Value,
 		Timestamp: sample.Timestamp,
@@ -562,18 +576,30 @@ func (s *memorySeriesStorage) Append(sample *clientmodel.Sample) {
 func (s *memorySeriesStorage) getOrCreateSeries(fp clientmodel.Fingerprint, m clientmodel.Metric) *memorySeries {
 	series, ok := s.fpToSeries.get(fp)
 	if !ok {
-		unarchived, firstTime, err := s.persistence.unarchiveMetric(fp)
+		var cds []*chunkDesc
+		var modTime time.Time
+		unarchived, err := s.persistence.unarchiveMetric(fp)
 		if err != nil {
-			log.Errorf("Error unarchiving fingerprint %v: %v", fp, err)
+			log.Errorf("Error unarchiving fingerprint %v (metric %v): %v", fp, m, err)
 		}
 		if unarchived {
 			s.seriesOps.WithLabelValues(unarchive).Inc()
+			// We have to load chunkDescs anyway to do anything with
+			// the series, so let's do it right now so that we don't
+			// end up with a series without any chunkDescs for a
+			// while (which is confusing as it makes the series
+			// appear as archived or purged).
+			cds, err = s.loadChunkDescs(fp, clientmodel.Latest)
+			if err != nil {
+				log.Errorf("Error loading chunk descs for fingerprint %v (metric %v): %v", fp, m, err)
+			}
+			modTime = s.persistence.seriesFileModTime(fp)
 		} else {
 			// This was a genuinely new series, so index the metric.
 			s.persistence.indexMetric(fp, m)
 			s.seriesOps.WithLabelValues(create).Inc()
 		}
-		series = newMemorySeries(m, !unarchived, firstTime)
+		series = newMemorySeries(m, cds, modTime)
 		s.fpToSeries.put(fp, series)
 		s.numSeries.Inc()
 	}
@@ -943,21 +969,8 @@ func (s *memorySeriesStorage) maintainMemorySeries(
 	if iOldestNotEvicted == -1 {
 		s.fpToSeries.del(fp)
 		s.numSeries.Dec()
-		// Make sure we have a head chunk descriptor (a freshly
-		// unarchived series has none).
-		if len(series.chunkDescs) == 0 {
-			cds, err := s.loadChunkDescs(fp, clientmodel.Latest)
-			if err != nil {
-				log.Errorf(
-					"Could not load chunk descriptors prior to archiving metric %v, metric will not be archived: %v",
-					series.metric, err,
-				)
-				return
-			}
-			series.chunkDescs = cds
-		}
 		if err := s.persistence.archiveMetric(
-			fp, series.metric, series.firstTime(), series.head().lastTime(),
+			fp, series.metric, series.firstTime(), series.lastTime,
 		); err != nil {
 			log.Errorf("Error archiving metric %v: %v", series.metric, err)
 			return
@@ -1154,6 +1167,7 @@ func (s *memorySeriesStorage) Describe(ch chan<- *prometheus.Desc) {
 	ch <- s.numSeries.Desc()
 	s.seriesOps.Describe(ch)
 	ch <- s.ingestedSamplesCount.Desc()
+	ch <- s.outOfOrderSamplesCount.Desc()
 	ch <- s.invalidPreloadRequestsCount.Desc()
 	ch <- numMemChunksDesc
 	s.maintainSeriesDuration.Describe(ch)
@@ -1178,6 +1192,7 @@ func (s *memorySeriesStorage) Collect(ch chan<- prometheus.Metric) {
 	ch <- s.numSeries
 	s.seriesOps.Collect(ch)
 	ch <- s.ingestedSamplesCount
+	ch <- s.outOfOrderSamplesCount
 	ch <- s.invalidPreloadRequestsCount
 	ch <- prometheus.MustNewConstMetric(
 		numMemChunksDesc,
diff --git a/storage/local/storage_test.go b/storage/local/storage_test.go
index da627ac742..e4dfd866e2 100644
--- a/storage/local/storage_test.go
+++ b/storage/local/storage_test.go
@@ -17,6 +17,7 @@ import (
 	"fmt"
 	"hash/fnv"
 	"math/rand"
+	"reflect"
 	"testing"
 	"testing/quick"
 	"time"
@@ -377,7 +378,7 @@ func TestRetentionCutoff(t *testing.T) {
 	s.WaitForIndexing()
 
 	var fp clientmodel.Fingerprint
-	for f := range s.fingerprintsForLabelPairs(metric.LabelPair{"job", "test"}) {
+	for f := range s.fingerprintsForLabelPairs(metric.LabelPair{Name: "job", Value: "test"}) {
 		fp = f
 		break
 	}
@@ -398,7 +399,7 @@ func TestRetentionCutoff(t *testing.T) {
 		t.Errorf("unexpected result for timestamp before retention period")
 	}
 
-	vals = it.RangeValues(metric.Interval{insertStart, now})
+	vals = it.RangeValues(metric.Interval{OldestInclusive: insertStart, NewestInclusive: now})
 	// We get 59 values here because the clientmodel.Now() is slightly later
 	// than our now.
 	if len(vals) != 59 {
@@ -408,7 +409,7 @@ func TestRetentionCutoff(t *testing.T) {
 		t.Errorf("unexpected timestamp for first sample: %v, expected %v", vals[0].Timestamp.Time(), expt.Time())
 	}
 
-	vals = it.BoundaryValues(metric.Interval{insertStart, now})
+	vals = it.BoundaryValues(metric.Interval{OldestInclusive: insertStart, NewestInclusive: now})
 	if len(vals) != 2 {
 		t.Errorf("expected 2 values but got %d", len(vals))
 	}
@@ -441,7 +442,7 @@ func TestDropMetrics(t *testing.T) {
 	}
 	s.WaitForIndexing()
 
-	fps := s.fingerprintsForLabelPairs(metric.LabelPair{clientmodel.MetricNameLabel, "test"})
+	fps := s.fingerprintsForLabelPairs(metric.LabelPair{Name: clientmodel.MetricNameLabel, Value: "test"})
 	if len(fps) != 2 {
 		t.Fatalf("unexpected number of fingerprints: %d", len(fps))
 	}
@@ -449,7 +450,7 @@ func TestDropMetrics(t *testing.T) {
 	var fpList clientmodel.Fingerprints
 	for fp := range fps {
 		it := s.NewIterator(fp)
-		if vals := it.RangeValues(metric.Interval{insertStart, now}); len(vals) != N {
+		if vals := it.RangeValues(metric.Interval{OldestInclusive: insertStart, NewestInclusive: now}); len(vals) != N {
 			t.Fatalf("unexpected number of samples: %d", len(vals))
 		}
 		fpList = append(fpList, fp)
@@ -458,34 +459,38 @@ func TestDropMetrics(t *testing.T) {
 	s.DropMetricsForFingerprints(fpList[0])
 	s.WaitForIndexing()
 
-	fps2 := s.fingerprintsForLabelPairs(metric.LabelPair{clientmodel.MetricNameLabel, "test"})
+	fps2 := s.fingerprintsForLabelPairs(metric.LabelPair{
+		Name: clientmodel.MetricNameLabel, Value: "test",
+	})
 	if len(fps2) != 1 {
 		t.Fatalf("unexpected number of fingerprints: %d", len(fps2))
 	}
 
 	it := s.NewIterator(fpList[0])
-	if vals := it.RangeValues(metric.Interval{insertStart, now}); len(vals) != 0 {
+	if vals := it.RangeValues(metric.Interval{OldestInclusive: insertStart, NewestInclusive: now}); len(vals) != 0 {
 		t.Fatalf("unexpected number of samples: %d", len(vals))
 	}
 	it = s.NewIterator(fpList[1])
-	if vals := it.RangeValues(metric.Interval{insertStart, now}); len(vals) != N {
+	if vals := it.RangeValues(metric.Interval{OldestInclusive: insertStart, NewestInclusive: now}); len(vals) != N {
 		t.Fatalf("unexpected number of samples: %d", len(vals))
 	}
 
 	s.DropMetricsForFingerprints(fpList...)
 	s.WaitForIndexing()
 
-	fps3 := s.fingerprintsForLabelPairs(metric.LabelPair{clientmodel.MetricNameLabel, "test"})
+	fps3 := s.fingerprintsForLabelPairs(metric.LabelPair{
+		Name: clientmodel.MetricNameLabel, Value: "test",
+	})
 	if len(fps3) != 0 {
 		t.Fatalf("unexpected number of fingerprints: %d", len(fps3))
 	}
 
 	it = s.NewIterator(fpList[0])
-	if vals := it.RangeValues(metric.Interval{insertStart, now}); len(vals) != 0 {
+	if vals := it.RangeValues(metric.Interval{OldestInclusive: insertStart, NewestInclusive: now}); len(vals) != 0 {
 		t.Fatalf("unexpected number of samples: %d", len(vals))
 	}
 	it = s.NewIterator(fpList[1])
-	if vals := it.RangeValues(metric.Interval{insertStart, now}); len(vals) != 0 {
+	if vals := it.RangeValues(metric.Interval{OldestInclusive: insertStart, NewestInclusive: now}); len(vals) != 0 {
 		t.Fatalf("unexpected number of samples: %d", len(vals))
 	}
 }
@@ -1405,3 +1410,50 @@ func verifyStorage(t testing.TB, s *memorySeriesStorage, samples clientmodel.Sam
 	}
 	return result
 }
+
+func TestAppendOutOfOrder(t *testing.T) {
+	s, closer := NewTestStorage(t, 1)
+	defer closer.Close()
+
+	m := clientmodel.Metric{
+		clientmodel.MetricNameLabel: "out_of_order",
+	}
+
+	for _, t := range []int{0, 2, 2, 1} {
+		s.Append(&clientmodel.Sample{
+			Metric:    m,
+			Timestamp: clientmodel.Timestamp(t),
+			Value:     clientmodel.SampleValue(t),
+		})
+	}
+
+	fp, err := s.mapper.mapFP(m.FastFingerprint(), m)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	pl := s.NewPreloader()
+	defer pl.Close()
+
+	err = pl.PreloadRange(fp, 0, 2, 5*time.Minute)
+	if err != nil {
+		t.Fatalf("error preloading chunks: %s", err)
+	}
+
+	it := s.NewIterator(fp)
+
+	want := metric.Values{
+		{
+			Timestamp: 0,
+			Value:     0,
+		},
+		{
+			Timestamp: 2,
+			Value:     2,
+		},
+	}
+	got := it.RangeValues(metric.Interval{OldestInclusive: 0, NewestInclusive: 2})
+	if !reflect.DeepEqual(want, got) {
+		t.Fatalf("want %v, got %v", want, got)
+	}
+}