diff --git a/data.c b/data.c
index 40c663d..4d892cc 100644
--- a/data.c
+++ b/data.c
@@ -14,13 +14,16 @@
 #include <sys/stat.h>
 #include <sys/file.h>
 #include <fcntl.h>
-
+#include <pthread.h>
 
 double disk_layout = 2.7;
 
+/* storage serializer */
+pthread_mutex_t data_mutex = {0};
 
 int snac_upgrade(d_char **error);
 
+
 int srv_open(char *basedir, int auto_upgrade)
 /* opens a server */
 {
@@ -29,6 +32,8 @@ int srv_open(char *basedir, int auto_upgrade)
     FILE *f;
     d_char *error = NULL;
 
+    pthread_mutex_init(&data_mutex, NULL);
+
     srv_basedir = xs_str_new(basedir);
 
     if (xs_endswith(srv_basedir, "/"))
@@ -121,6 +126,8 @@ void srv_free(void)
     xs_free(srv_basedir);
     xs_free(srv_config);
     xs_free(srv_baseurl);
+
+    pthread_mutex_destroy(&data_mutex);
 }
 
 
@@ -250,6 +257,8 @@ int index_add_md5(const char *fn, const char *md5)
     int status = 201; /* Created */
     FILE *f;
 
+    pthread_mutex_lock(&data_mutex);
+
     if ((f = fopen(fn, "a")) != NULL) {
         flock(fileno(f), LOCK_EX);
 
@@ -262,6 +271,8 @@ int index_add_md5(const char *fn, const char *md5)
     else
         status = 500;
 
+    pthread_mutex_unlock(&data_mutex);
+
     return status;
 }
 
@@ -280,6 +291,8 @@ int index_del_md5(const char *fn, const char *md5)
     int status = 404;
     FILE *i, *o;
 
+    pthread_mutex_lock(&data_mutex);
+
     if ((i = fopen(fn, "r")) != NULL) {
         flock(fileno(i), LOCK_EX);
 
@@ -309,6 +322,8 @@ int index_del_md5(const char *fn, const char *md5)
     else
         status = 500;
 
+    pthread_mutex_unlock(&data_mutex);
+
     return status;
 }