diff --git a/cmd/backoffice/fileserver.go b/cmd/backoffice/fileserver.go
index 8005005..3efd62c 100644
--- a/cmd/backoffice/fileserver.go
+++ b/cmd/backoffice/fileserver.go
@@ -8,17 +8,20 @@ import (
 	"net/http"
 	"os"
 	"path/filepath"
+	"regexp"
 	"sort"
 	"strconv"
 	"strings"
 	"time"
 
+	"git.tornberg.me/go-cart-actor/pkg/actor"
 	"git.tornberg.me/go-cart-actor/pkg/cart"
 )
 
 type FileServer struct {
 	// Define fields here
 	dataDir string
+	storage actor.LogStorage[cart.CartGrain]
 }
 
 func NewFileServer(dataDir string) *FileServer {
@@ -27,21 +30,29 @@ func NewFileServer(dataDir string) *FileServer {
 	}
 }
 
+func isValidId(id string) (uint64, bool) {
+	if nr, err := strconv.ParseUint(id, 10, 64); err == nil {
+		return nr, true
+	}
+	if nr, ok := cart.ParseCartId(id); ok {
+		return uint64(nr), true
+	}
+	return 0, false
+}
+
 func isValidFileId(name string) (uint64, bool) {
 
 	parts := strings.Split(name, ".")
 	if len(parts) > 1 && parts[1] == "events" {
 		idStr := parts[0]
-		if _, err := strconv.ParseUint(idStr, 10, 64); err != nil {
-			return 0, false
-		}
-		if id, err := strconv.ParseUint(idStr, 10, 64); err == nil {
-			return id, true
-		}
+
+		return isValidId(idStr)
 	}
 	return 0, false
 }
 
+var cartFileRe = regexp.MustCompile(`^(\d+)\.events\.log$`)
+
 func listCartFiles(dir string) ([]CartFileInfo, error) {
 	entries, err := os.ReadDir(dir)
 	if err != nil {
@@ -76,20 +87,20 @@ func listCartFiles(dir string) ([]CartFileInfo, error) {
 	return out, nil
 }
 
-func readRawLogLines(path string) ([]string, error) {
+func readRawLogLines(path string) ([]json.RawMessage, error) {
 	fh, err := os.Open(path)
 	if err != nil {
 		return nil, err
 	}
 	defer fh.Close()
-	lines := make([]string, 0, 64)
+	lines := make([]json.RawMessage, 0, 64)
 	s := bufio.NewScanner(fh)
 	// increase buffer to handle larger JSON lines
 	buf := make([]byte, 0, 1024*1024)
 	s.Buffer(buf, 1024*1024)
 	for s.Scan() {
-		line := strings.TrimSpace(s.Text())
-		if line == "" {
+		line := s.Bytes()
+		if line == nil {
 			continue
 		}
 		lines = append(lines, line)
@@ -122,40 +133,41 @@ func (fs *FileServer) CartsHandler(w http.ResponseWriter, r *http.Request) {
 	})
 }
 
+type JsonError struct {
+	Error string `json:"error"`
+}
+
 func (fs *FileServer) CartHandler(w http.ResponseWriter, r *http.Request) {
 	idStr := r.PathValue("id")
 	if idStr == "" {
-		writeJSON(w, http.StatusBadRequest, map[string]string{"error": "missing id"})
+		writeJSON(w, http.StatusBadRequest, JsonError{Error: "missing id"})
 		return
 	}
-
-	id, err := strconv.ParseUint(idStr, 10, 64)
-	if err != nil {
-		if cartId, ok := cart.ParseCartId(idStr); !ok {
-			writeJSON(w, http.StatusBadRequest, map[string]string{"error": "invalid id"})
-			return
-		} else {
-			id = uint64(cartId)
-		}
+	id, ok := isValidId(idStr)
+	if !ok {
+		writeJSON(w, http.StatusBadRequest, JsonError{Error: "invalid id"})
 	}
 	// reconstruct state from event log if present
 	grain := cart.NewCartGrain(id, time.Now())
-	if globalDisk != nil {
-		_ = globalDisk.LoadEvents(id, grain)
+
+	err := fs.storage.LoadEvents(id, grain)
+	if err != nil {
+		writeJSON(w, http.StatusInternalServerError, JsonError{Error: err.Error()})
+		return
 	}
 
 	path := filepath.Join(fs.dataDir, fmt.Sprintf("%d.events.log", id))
 	info, err := os.Stat(path)
 	if err != nil && errors.Is(err, os.ErrNotExist) {
-		writeJSON(w, http.StatusNotFound, map[string]string{"error": "cart not found"})
+		writeJSON(w, http.StatusNotFound, JsonError{Error: "cart not found"})
 		return
 	} else if err != nil {
-		writeJSON(w, http.StatusInternalServerError, map[string]string{"error": err.Error()})
+		writeJSON(w, http.StatusInternalServerError, JsonError{Error: err.Error()})
 		return
 	}
 	lines, err := readRawLogLines(path)
 	if err != nil {
-		writeJSON(w, http.StatusInternalServerError, map[string]string{"error": err.Error()})
+		writeJSON(w, http.StatusInternalServerError, JsonError{Error: err.Error()})
 		return
 	}
 	writeJSON(w, http.StatusOK, map[string]any{
@@ -167,6 +179,7 @@ func (fs *FileServer) CartHandler(w http.ResponseWriter, r *http.Request) {
 			"size":     info.Size(),
 			"modified": info.ModTime(),
 			"path":     path,
+			"system":   info.Sys(),
 		},
 	})
 }
diff --git a/cmd/backoffice/main.go b/cmd/backoffice/main.go
index 1b1c03b..8a72597 100644
--- a/cmd/backoffice/main.go
+++ b/cmd/backoffice/main.go
@@ -6,7 +6,6 @@ import (
 	"log"
 	"net/http"
 	"os"
-	"regexp"
 	"time"
 
 	actor "git.tornberg.me/go-cart-actor/pkg/actor"
@@ -30,8 +29,6 @@ func envOrDefault(key, def string) string {
 	return def
 }
 
-var cartFileRe = regexp.MustCompile(`^(\d+)\.events\.log$`)
-
 var globalDisk *actor.DiskStorage[cart.CartGrain]
 
 func startMutationConsumer(ctx context.Context, conn *amqp.Connection, hub *Hub) error {
diff --git a/cmd/cart/main.go b/cmd/cart/main.go
index cd6d558..d1e71c5 100644
--- a/cmd/cart/main.go
+++ b/cmd/cart/main.go
@@ -99,6 +99,11 @@ type MutationContext struct {
 	VoucherService voucher.Service
 }
 
+type CartChangeEvent struct {
+	CartId    cart.CartId         `json:"cartId"`
+	Mutations []actor.ApplyResult `json:"mutations"`
+}
+
 func main() {
 
 	controlPlaneConfig := actor.DefaultServerConfig()
@@ -138,7 +143,12 @@ func main() {
 		fmt.Errorf("failed to connect to RabbitMQ: %w", err)
 	}
 
-	amqpListener := actor.NewAmqpListener(conn)
+	amqpListener := actor.NewAmqpListener(conn, func(id uint64, msg []actor.ApplyResult) (any, error) {
+		return &CartChangeEvent{
+			CartId:    cart.CartId(id),
+			Mutations: msg,
+		}, nil
+	})
 	amqpListener.DefineTopics()
 	pool.AddListener(amqpListener)
 
diff --git a/pkg/actor/disk_storage.go b/pkg/actor/disk_storage.go
index 08daf71..deff401 100644
--- a/pkg/actor/disk_storage.go
+++ b/pkg/actor/disk_storage.go
@@ -10,8 +10,6 @@ import (
 	"time"
 
 	"github.com/gogo/protobuf/proto"
-	"github.com/matst80/slask-finder/pkg/messaging"
-	amqp "github.com/rabbitmq/amqp091-go"
 )
 
 type QueueEvent struct {
@@ -31,46 +29,6 @@ type LogStorage[V any] interface {
 	AppendMutations(id uint64, msg ...proto.Message) error
 }
 
-type LogListener interface {
-	AppendMutations(id uint64, msg ...ApplyResult)
-}
-
-type AmqpListener struct {
-	conn *amqp.Connection
-}
-
-func NewAmqpListener(conn *amqp.Connection) *AmqpListener {
-	return &AmqpListener{
-		conn: conn,
-	}
-}
-
-func (l *AmqpListener) DefineTopics() {
-	ch, err := l.conn.Channel()
-	if err != nil {
-		log.Fatalf("Failed to open a channel: %v", err)
-	}
-	defer ch.Close()
-	if err := messaging.DefineTopic(ch, "cart", "mutation"); err != nil {
-		log.Fatalf("Failed to declare topic mutation: %v", err)
-	}
-}
-
-type CartEvent struct {
-	Id        uint64        `json:"id"`
-	Mutations []ApplyResult `json:"mutations"`
-}
-
-func (l *AmqpListener) AppendMutations(id uint64, msg ...ApplyResult) {
-	err := messaging.SendChange(l.conn, "cart", "mutation", &CartEvent{
-		Id:        id,
-		Mutations: msg,
-	})
-	if err != nil {
-		log.Printf("Failed to send mutation event: %v", err)
-	}
-}
-
 func NewDiskStorage[V any](path string, registry MutationRegistry) *DiskStorage[V] {
 	return &DiskStorage[V]{
 		StateStorage: NewState(registry),
diff --git a/pkg/actor/log_listerner.go b/pkg/actor/log_listerner.go
new file mode 100644
index 0000000..3990c77
--- /dev/null
+++ b/pkg/actor/log_listerner.go
@@ -0,0 +1,47 @@
+package actor
+
+import (
+	"log"
+
+	"github.com/matst80/slask-finder/pkg/messaging"
+	amqp "github.com/rabbitmq/amqp091-go"
+)
+
+type LogListener interface {
+	AppendMutations(id uint64, msg ...ApplyResult)
+}
+
+type AmqpListener struct {
+	conn        *amqp.Connection
+	transformer func(id uint64, msg []ApplyResult) (any, error)
+}
+
+func NewAmqpListener(conn *amqp.Connection, transformer func(id uint64, msg []ApplyResult) (any, error)) *AmqpListener {
+	return &AmqpListener{
+		conn:        conn,
+		transformer: transformer,
+	}
+}
+
+func (l *AmqpListener) DefineTopics() {
+	ch, err := l.conn.Channel()
+	if err != nil {
+		log.Fatalf("Failed to open a channel: %v", err)
+	}
+	defer ch.Close()
+	if err := messaging.DefineTopic(ch, "cart", "mutation"); err != nil {
+		log.Fatalf("Failed to declare topic mutation: %v", err)
+	}
+}
+
+func (l *AmqpListener) AppendMutations(id uint64, msg ...ApplyResult) {
+	data, err := l.transformer(id, msg)
+	if err != nil {
+		log.Printf("Failed to transform mutation event: %v", err)
+		return
+	}
+	err = messaging.SendChange(l.conn, "cart", "mutation", data)
+	if err != nil {
+		log.Printf("Failed to send mutation event: %v", err)
+	}
+}