diff --git a/internal/memstore/chunks.go b/internal/memstore/chunks.go
index a0ce97a..b84adaf 100644
--- a/internal/memstore/chunks.go
+++ b/internal/memstore/chunks.go
@@ -72,8 +72,6 @@ func (c *chunk) firstWrite() int64 {
 	return c.start + (c.frequency / 2)
 }
 
-func (c *chunk) close() {}
-
 // func interpolate(idx int, data []Float) Float {
 // 	if idx == 0 || idx+1 == len(data) {
 // 		return NaN
diff --git a/internal/memstore/memstore.go b/internal/memstore/memstore.go
index 595d7fe..a87147c 100644
--- a/internal/memstore/memstore.go
+++ b/internal/memstore/memstore.go
@@ -1,6 +1,7 @@
 package memstore
 
 import (
+	"errors"
 	"sync"
 
 	"github.com/ClusterCockpit/cc-metric-store/internal/types"
@@ -66,6 +67,22 @@ func (l *Level) findLevelOrCreate(selector []string, nMetrics int) *Level {
 	return child.findLevelOrCreate(selector[1:], nMetrics)
 }
 
+func (l *Level) findLevel(selector []string) *Level {
+	if len(selector) == 0 {
+		return l
+	}
+
+	l.lock.RLock()
+	defer l.lock.RUnlock()
+
+	lvl := l.sublevels[selector[0]]
+	if lvl == nil {
+		return nil
+	}
+
+	return lvl.findLevel(selector[1:])
+}
+
 func (l *Level) free(t int64) (delme bool, n int) {
 	l.lock.Lock()
 	defer l.lock.Unlock()
@@ -171,3 +188,133 @@ func (m *MemoryStore) WriteToLevel(l *Level, selector []string, ts int64, metric
 	}
 	return nil
 }
+
+func (m *MemoryStore) Free(t int64) int {
+	_, n := m.root.free(t)
+	return n
+}
+
+func (l *Level) findBuffers(selector types.Selector, offset int, f func(c *chunk) error) error {
+	l.lock.RLock()
+	defer l.lock.RUnlock()
+
+	if len(selector) == 0 {
+		b := l.metrics[offset]
+		if b != nil {
+			return f(b)
+		}
+
+		for _, lvl := range l.sublevels {
+			err := lvl.findBuffers(nil, offset, f)
+			if err != nil {
+				return err
+			}
+		}
+		return nil
+	}
+
+	sel := selector[0]
+	if len(sel.String) != 0 && l.sublevels != nil {
+		lvl, ok := l.sublevels[sel.String]
+		if ok {
+			err := lvl.findBuffers(selector[1:], offset, f)
+			if err != nil {
+				return err
+			}
+		}
+		return nil
+	}
+
+	if sel.Group != nil && l.sublevels != nil {
+		for _, key := range sel.Group {
+			lvl, ok := l.sublevels[key]
+			if ok {
+				err := lvl.findBuffers(selector[1:], offset, f)
+				if err != nil {
+					return err
+				}
+			}
+		}
+		return nil
+	}
+
+	if sel.Any && l.sublevels != nil {
+		for _, lvl := range l.sublevels {
+			if err := lvl.findBuffers(selector[1:], offset, f); err != nil {
+				return err
+			}
+		}
+		return nil
+	}
+
+	return nil
+}
+
+var (
+	ErrNoData           error = errors.New("no data for this metric/level")
+	ErrDataDoesNotAlign error = errors.New("data from lower granularities does not align")
+)
+
+// Returns all values for metric `metric` from `from` to `to` for the selected level(s).
+// If the level does not hold the metric itself, the data will be aggregated recursively from the children.
+// The second and third return value are the actual from/to for the data. Those can be different from
+// the range asked for if no data was available.
+func (m *MemoryStore) Read(selector types.Selector, metric string, from, to int64) ([]types.Float, int64, int64, error) {
+	if from > to {
+		return nil, 0, 0, errors.New("invalid time range")
+	}
+
+	mc, ok := m.metrics[metric]
+	if !ok {
+		return nil, 0, 0, errors.New("unkown metric: " + metric)
+	}
+
+	n, data := 0, make([]types.Float, (to-from)/mc.Frequency+1)
+	err := m.root.findBuffers(selector, mc.Offset, func(c *chunk) error {
+		cdata, cfrom, cto, err := c.read(from, to, data)
+		if err != nil {
+			return err
+		}
+
+		if n == 0 {
+			from, to = cfrom, cto
+		} else if from != cfrom || to != cto || len(data) != len(cdata) {
+			missingfront, missingback := int((from-cfrom)/mc.Frequency), int((to-cto)/mc.Frequency)
+			if missingfront != 0 {
+				return ErrDataDoesNotAlign
+			}
+
+			newlen := len(cdata) - missingback
+			if newlen < 1 {
+				return ErrDataDoesNotAlign
+			}
+			cdata = cdata[0:newlen]
+			if len(cdata) != len(data) {
+				return ErrDataDoesNotAlign
+			}
+
+			from, to = cfrom, cto
+		}
+
+		data = cdata
+		n += 1
+		return nil
+	})
+
+	if err != nil {
+		return nil, 0, 0, err
+	} else if n == 0 {
+		return nil, 0, 0, errors.New("metric or host not found")
+	} else if n > 1 {
+		if mc.Aggregation == types.AvgAggregation {
+			normalize := 1. / types.Float(n)
+			for i := 0; i < len(data); i++ {
+				data[i] *= normalize
+			}
+		} else if mc.Aggregation != types.SumAggregation {
+			return nil, 0, 0, errors.New("invalid aggregation")
+		}
+	}
+
+	return data, from, to, nil
+}
diff --git a/internal/types/selector.go b/internal/types/selector.go
new file mode 100644
index 0000000..58b3631
--- /dev/null
+++ b/internal/types/selector.go
@@ -0,0 +1,51 @@
+package types
+
+import (
+	"encoding/json"
+	"errors"
+)
+
+type SelectorElement struct {
+	Any    bool
+	String string
+	Group  []string
+}
+
+func (se *SelectorElement) UnmarshalJSON(input []byte) error {
+	if input[0] == '"' {
+		if err := json.Unmarshal(input, &se.String); err != nil {
+			return err
+		}
+
+		if se.String == "*" {
+			se.Any = true
+			se.String = ""
+		}
+
+		return nil
+	}
+
+	if input[0] == '[' {
+		return json.Unmarshal(input, &se.Group)
+	}
+
+	return errors.New("the Go SelectorElement type can only be a string or an array of strings")
+}
+
+func (se *SelectorElement) MarshalJSON() ([]byte, error) {
+	if se.Any {
+		return []byte("\"*\""), nil
+	}
+
+	if se.String != "" {
+		return json.Marshal(se.String)
+	}
+
+	if se.Group != nil {
+		return json.Marshal(se.Group)
+	}
+
+	return nil, errors.New("a Go Selector must be a non-empty string or a non-empty slice of strings")
+}
+
+type Selector []SelectorElement
diff --git a/selector.go b/selector.go
deleted file mode 100644
index 25fe209..0000000
--- a/selector.go
+++ /dev/null
@@ -1,123 +0,0 @@
-package main
-
-import (
-	"encoding/json"
-	"errors"
-)
-
-type SelectorElement struct {
-	Any    bool
-	String string
-	Group  []string
-}
-
-func (se *SelectorElement) UnmarshalJSON(input []byte) error {
-	if input[0] == '"' {
-		if err := json.Unmarshal(input, &se.String); err != nil {
-			return err
-		}
-
-		if se.String == "*" {
-			se.Any = true
-			se.String = ""
-		}
-
-		return nil
-	}
-
-	if input[0] == '[' {
-		return json.Unmarshal(input, &se.Group)
-	}
-
-	return errors.New("the Go SelectorElement type can only be a string or an array of strings")
-}
-
-func (se *SelectorElement) MarshalJSON() ([]byte, error) {
-	if se.Any {
-		return []byte("\"*\""), nil
-	}
-
-	if se.String != "" {
-		return json.Marshal(se.String)
-	}
-
-	if se.Group != nil {
-		return json.Marshal(se.Group)
-	}
-
-	return nil, errors.New("a Go Selector must be a non-empty string or a non-empty slice of strings")
-}
-
-type Selector []SelectorElement
-
-func (l *level) findLevel(selector []string) *level {
-	if len(selector) == 0 {
-		return l
-	}
-
-	l.lock.RLock()
-	defer l.lock.RUnlock()
-
-	lvl := l.children[selector[0]]
-	if lvl == nil {
-		return nil
-	}
-
-	return lvl.findLevel(selector[1:])
-}
-
-func (l *level) findBuffers(selector Selector, offset int, f func(b *buffer) error) error {
-	l.lock.RLock()
-	defer l.lock.RUnlock()
-
-	if len(selector) == 0 {
-		b := l.metrics[offset]
-		if b != nil {
-			return f(b)
-		}
-
-		for _, lvl := range l.children {
-			err := lvl.findBuffers(nil, offset, f)
-			if err != nil {
-				return err
-			}
-		}
-		return nil
-	}
-
-	sel := selector[0]
-	if len(sel.String) != 0 && l.children != nil {
-		lvl, ok := l.children[sel.String]
-		if ok {
-			err := lvl.findBuffers(selector[1:], offset, f)
-			if err != nil {
-				return err
-			}
-		}
-		return nil
-	}
-
-	if sel.Group != nil && l.children != nil {
-		for _, key := range sel.Group {
-			lvl, ok := l.children[key]
-			if ok {
-				err := lvl.findBuffers(selector[1:], offset, f)
-				if err != nil {
-					return err
-				}
-			}
-		}
-		return nil
-	}
-
-	if sel.Any && l.children != nil {
-		for _, lvl := range l.children {
-			if err := lvl.findBuffers(selector[1:], offset, f); err != nil {
-				return err
-			}
-		}
-		return nil
-	}
-
-	return nil
-}