diff --git a/internal/storage/db.go b/internal/storage/db.go
index 060f0c0..8c9ff35 100644
--- a/internal/storage/db.go
+++ b/internal/storage/db.go
@@ -10,6 +10,14 @@ const (
 	DATATYPE_USERSUB = 64
 )
 
+// PrefixDb interface abstracts the database operations.
+type PrefixDb interface {
+	Get(ctx context.Context, key []byte) ([]byte, error)
+	Put(ctx context.Context, key []byte, val []byte) error
+}
+
+var _ PrefixDb = (*SubPrefixDb)(nil)
+
 type SubPrefixDb struct {
 	store db.Db
 	pfx   []byte
@@ -29,11 +37,7 @@ func (s *SubPrefixDb) toKey(k []byte) []byte {
 func (s *SubPrefixDb) Get(ctx context.Context, key []byte) ([]byte, error) {
 	s.store.SetPrefix(DATATYPE_USERSUB)
 	key = s.toKey(key)
-	v, err := s.store.Get(ctx, key)
-	if err != nil {
-		return nil, err
-	}
-	return v, nil
+	return s.store.Get(ctx, key)
 }
 
 func (s *SubPrefixDb) Put(ctx context.Context, key []byte, val []byte) error {