diff --git a/include/clixon_custom.h b/include/clixon_custom.h
index eb8d56b8..bc37338d 100644
--- a/include/clixon_custom.h
+++ b/include/clixon_custom.h
@@ -233,3 +233,16 @@
  * A more intelligent algorithm is needed
  */
 #define XML_DEFAULT_WHEN_TWICE
+
+/*! If set, make optimized lookup of yspec + namespace -> module
+ *
+ * see yang_find_module_by_namespace
+ */
+#define OPTIMIZE_YSPEC_NAMESPACE
+
+/*! If set, make optimization of non-presence default container
+ *
+ * Save the default XML in YANG and reuse next time
+ * see xml_default
+ */
+#define OPTIMIZE_NO_PRESENCE_CONTAINER
diff --git a/lib/clixon/clixon_map.h b/lib/clixon/clixon_map.h
index 66d9a666..7f450045 100644
--- a/lib/clixon/clixon_map.h
+++ b/lib/clixon/clixon_map.h
@@ -54,19 +54,27 @@ static const map_str2int atmap[] = {
  * @see clicon_str2int
  */
 struct map_str2int{
-    char         *ms_str;
-    int           ms_int;
+    char *ms_str;
+    int   ms_int;
 };
 typedef struct map_str2int map_str2int;
 
 /*! Struct used to map between two strings.
  */
 struct map_str2str{
-    char         *ms_s0;
-    char         *ms_s1;
+    char *ms_s0;
+    char *ms_s1;
 };
 typedef struct map_str2str map_str2str;
 
+/*! Struct used to map from string to pointer
+ */
+struct map_str2ptr{
+    char *mp_str;
+    void *mp_ptr;
+};
+typedef struct map_str2ptr map_str2ptr;
+
 /*! Map from ptr to ptr
  */
 struct map_ptr2ptr{
@@ -82,6 +90,9 @@ const char *clicon_int2str(const map_str2int *mstab, int i);
 int         clicon_str2int(const map_str2int *mstab, char *str);
 int         clicon_str2int_search(const map_str2int *mstab, char *str, int upper);
 char       *clicon_str2str(const map_str2str *mstab, char *str);
+void        clixon_str2ptr_sort(map_str2ptr *mptab, size_t len);
+void       *clixon_str2ptr(map_str2ptr *mptab, char *str, size_t len);
+int         clixon_str2ptr_print(FILE *f, map_str2ptr *mptab);
 void       *clixon_ptr2ptr(map_ptr2ptr *mptab, void *ptr);
 int         clixon_ptr2ptr_add(map_ptr2ptr **mptab, void *ptr0, void *ptr1);
 
diff --git a/lib/clixon/clixon_yang.h b/lib/clixon/clixon_yang.h
index 7fd828b6..16f6bbb3 100644
--- a/lib/clixon/clixon_yang.h
+++ b/lib/clixon/clixon_yang.h
@@ -354,6 +354,10 @@ int        yang_sort_subelements(yang_stmt *ys);
 int        yang_single_child_type(yang_stmt *ys, enum rfc_6020 subkeyw);
 void      *yang_action_cb_get(yang_stmt *ys);
 int        yang_action_cb_add(yang_stmt *ys, void *rc);
+#ifdef OPTIMIZE_NO_PRESENCE_CONTAINER
+void      *yang_nopresence_cache_get(yang_stmt *ys);
+int        yang_nopresence_cache_set(yang_stmt *ys, void *x);
+#endif
 int        ys_populate_feature(clixon_handle h, yang_stmt *ys);
 int        yang_init(clixon_handle h);
 int        yang_start(clixon_handle h);
diff --git a/lib/clixon/clixon_yang_parse_lib.h b/lib/clixon/clixon_yang_parse_lib.h
index f97e337b..8b980d5a 100644
--- a/lib/clixon/clixon_yang_parse_lib.h
+++ b/lib/clixon/clixon_yang_parse_lib.h
@@ -65,5 +65,10 @@ int        yang_spec_load_dir(clixon_handle h, char *dir, yang_stmt *yspec);
 int        ys_parse_date_arg(char *datearg, uint32_t *dateint);
 cg_var    *ys_parse(yang_stmt *ys, enum cv_type cvtype);
 int        ys_parse_sub(yang_stmt *ys, const char *filename, char *extra);
+#ifdef OPTIMIZE_YSPEC_NAMESPACE
+int        yspec_nscache_clear(yang_stmt *yspec);
+yang_stmt *yspec_nscache_get(yang_stmt *yspec, char *ns);
+int        yspec_nscache_new(yang_stmt *yspec);
+#endif
 
 #endif  /* _CLIXON_YANG_LIB_H_ */
diff --git a/lib/src/clixon_map.c b/lib/src/clixon_map.c
index 05e22015..1d99edf7 100644
--- a/lib/src/clixon_map.c
+++ b/lib/src/clixon_map.c
@@ -55,6 +55,7 @@
 #include "clixon_yang.h"
 #include "clixon_xml.h"
 #include "clixon_err.h"
+#include "clixon_string.h"
 
 /*! Map from int to string using str2int map
  *
@@ -116,9 +117,9 @@ str2int_search1(const map_str2int *mstab,
                 int                len,
                 int               *found)
 {
-    const struct map_str2int *ms;
-    int                       mid;
-    int                       cmp;
+    const map_str2int *ms;
+    int                mid;
+    int                cmp;
 
     if (upper < low)
         return 0; /* not found */
@@ -136,10 +137,58 @@ str2int_search1(const map_str2int *mstab,
         return str2int_search1(mstab, str, mid+1, upper, len, found);
 }
 
+/*! Map from string to ptr using binary (alphatical) search
+ *
+ * Assumes sorted strings, tree search. If two are equal take first
+ * @param[in]  ms    String, integer map
+ * @param[in]  str   Input string
+ * @param[in]  low   Lower bound index
+ * @param[in]  upper Upper bound index
+ * @param[in]  len   Length of array (max)
+ * @param[out] found element
+ * @retval     1     Found with "found" value set.
+ * @retval     0     Not found
+
+ */
+static int
+str2ptr_search1(const map_str2ptr *mptab,
+                char              *str,
+                size_t             low,
+                size_t             upper,
+                size_t             len,
+                map_str2ptr      **found)
+{
+    const map_str2ptr *mp;
+    int                mid;
+    int                cmp;
+    int                i;
+
+    if (upper < low)
+        return 0; /* not found */
+    mid = (low + upper) / 2;
+    if (mid >= len)  /* beyond range */
+        return 0; /* not found */
+    mp = &mptab[mid];
+    if ((cmp = clicon_strcmp(str, mp->mp_str)) == 0){
+        i = mid;
+        while (i >= 0 && clicon_strcmp(str, mptab[i].mp_str) == 0){
+            mp = &mptab[i];
+            i--;
+        }
+        *found = (map_str2ptr *)mp;
+        return 1; /* found */
+    }
+    else if (cmp < 0)
+        return str2ptr_search1(mptab, str, low, mid-1, len, found);
+    else
+        return str2ptr_search1(mptab, str, mid+1, upper, len, found);
+}
+
 /*! Map from string to int using str2int map
  *
  * @param[in] ms   String, integer map
  * @param[in] str  Input string
+ * @param[in] len
  * @retval    int  Value
  * @retval   -1    Error, not found
  * @note Assumes sorted strings, tree search
@@ -176,6 +225,67 @@ clicon_str2str(const map_str2str *mstab,
     return NULL;
 }
 
+static int
+str2ptr_qsort(const void* arg1,
+              const void* arg2)
+{
+    map_str2ptr *mp1 = (map_str2ptr*)arg1;
+    map_str2ptr *mp2 = (map_str2ptr*)arg2;
+    int          eq;
+    yang_stmt   *yrev;
+    char        *rev1 = NULL;
+    char        *rev2 = NULL;
+
+    eq = clicon_strcmp(mp1->mp_str, mp2->mp_str);
+    if (0 && eq == 0){
+        if ((yrev = yang_find(mp1->mp_ptr, Y_REVISION, NULL)) != NULL)
+            rev1 = yang_argument_get(yrev);
+        if ((yrev = yang_find(mp2->mp_ptr, Y_REVISION, NULL)) != NULL)
+            rev2 = yang_argument_get(yrev);
+        eq = clicon_strcmp(rev1, rev2);
+    }
+    return eq;
+}
+
+void
+clixon_str2ptr_sort(map_str2ptr *mptab,
+                    size_t       len)
+{
+    qsort(mptab, len, sizeof(*mptab), str2ptr_qsort);
+}
+
+/*! Map from string to string using str2str map
+ *
+ * @param[in] mptab String to ptr map
+ * @param[in] str   Input string
+ * @retval    ptr   Output pointer
+ * @retval    NULL  Error, not found
+ */
+void*
+clixon_str2ptr(map_str2ptr *mptab,
+               char         *str,
+               size_t        len)
+{
+    map_str2ptr *mp = NULL;
+
+    if (str2ptr_search1(mptab, str, 0, len, len, &mp))
+        return mp->mp_ptr;
+    return NULL; /* not found */
+}
+
+int
+clixon_str2ptr_print(FILE        *f,
+                     map_str2ptr *mptab)
+{
+    map_str2ptr *mp = NULL;
+    int          i;
+
+    i = 0;
+    for (mp = &mptab[0]; mp->mp_str; mp++)
+        fprintf(f, "%d %s %p\n", i++, mp->mp_str, mp->mp_ptr);
+    return 0;
+}
+
 /*! Map from pointer to pointer using mptab map
  *
  * @param[in] mptab Ptr to ptr map
diff --git a/lib/src/clixon_xml_default.c b/lib/src/clixon_xml_default.c
index 1186f98f..1a90c9e9 100644
--- a/lib/src/clixon_xml_default.c
+++ b/lib/src/clixon_xml_default.c
@@ -297,6 +297,9 @@ xml_default(yang_stmt *yt,
     int        retval = -1;
     yang_stmt *yc;
     cxobj     *xc;
+#ifdef OPTIMIZE_NO_PRESENCE_CONTAINER
+    cxobj     *xc1;
+#endif
     int        top = 0; /* Top symbol (set default namespace) */
     int        create = 0;
     int        nr = 0;
@@ -361,19 +364,37 @@ xml_default(yang_stmt *yt,
                      * defaults.
                      */
                     if (xml_find_type(xt, NULL, yang_argument_get(yc), CX_ELMNT) == NULL){
-                        /* No such container exist, recursively try if needed */
-                        if (xml_nopresence_try(yc, state, &create) < 0)
-                            goto done;
-                        if (create){
-                            /* Retval shows there is a default value need to create the
-                             * container */
-                            if (xml_default_create1(yc, xt, &xc) < 0)
+#ifdef OPTIMIZE_NO_PRESENCE_CONTAINER
+                        if ((xc = yang_nopresence_cache_get(yc)) != NULL){
+                            if ((xc1 = xml_dup(xc)) == NULL)
+                                goto done;
+                            if (xml_addsub(xt, xc1) < 0)
                                 goto done;
                             xml_sort(xt);
-                            /* Then call it recursively */
-                            if (xml_default(yc, xc, state) < 0)
-                                goto done;
                         }
+                        else
+#endif
+                            {
+                                /* No such container exist, recursively try if needed */
+                                if (xml_nopresence_try(yc, state, &create) < 0)
+                                    goto done;
+                                if (create){
+                                    /* Retval shows there is a default value need to create the
+                                     * container */
+                                    if (xml_default_create1(yc, xt, &xc) < 0)
+                                        goto done;
+                                    xml_sort(xt);
+                                    /* Then call it recursively */
+                                    if (xml_default(yc, xc, state) < 0)
+                                        goto done;
+#ifdef OPTIMIZE_NO_PRESENCE_CONTAINER
+                                    if ((xc1 = xml_dup(xc)) == NULL)
+                                        goto done;
+                                    if (yang_nopresence_cache_set(yc, xc1) < 0)
+                                        goto done;
+#endif
+                                }
+                            }
                     }
                 }
                 break;
diff --git a/lib/src/clixon_yang.c b/lib/src/clixon_yang.c
index 5908c514..67c10c3c 100644
--- a/lib/src/clixon_yang.c
+++ b/lib/src/clixon_yang.c
@@ -1090,6 +1090,19 @@ ys_free1(yang_stmt *ys,
         if (ys->ys_filename)
             free(ys->ys_filename);
         break;
+#ifdef OPTIMIZE_NO_PRESENCE_CONTAINER
+    case Y_CONTAINER:
+        if (ys->ys_nopres_cache)
+            xml_free(ys->ys_nopres_cache);
+        break;
+#endif
+#ifdef OPTIMIZE_YSPEC_NAMESPACE
+    case Y_SPEC:
+        if (ys->ys_nscache)
+            free(ys->ys_nscache);
+        break;
+#endif
+
     default:
         break;
     }
@@ -1220,6 +1233,11 @@ yn_realloc(yang_stmt *yn)
         return -1;
     }
     yn->ys_stmt[yn->ys_len - 1] = NULL; /* init field */
+#ifdef OPTIMIZE_YSPEC_NAMESPACE
+    if (yn->ys_keyword == Y_SPEC && yn->ys_nscache){         /* Clear cache */
+        yspec_nscache_clear(yn);
+    }
+#endif
     return 0;
 }
 
@@ -1336,6 +1354,16 @@ ys_cp_one(yang_stmt *ynew,
         if (yang_typecache_get(yold)) /* Dont copy type cache, use only original */
             yang_typecache_set(ynew, NULL);
         break;
+#ifdef OPTIMIZE_NO_PRESENCE_CONTAINER
+    case Y_CONTAINER:
+        yold->ys_nopres_cache = NULL;
+        break;
+#endif
+#ifdef OPTIMIZE_YSPEC_NAMESPACE
+    case Y_SPEC:
+        yold->ys_nscache = NULL;
+        break;
+#endif
     default:
         break;
     }
@@ -4034,11 +4062,12 @@ int
 yang_config(yang_stmt *ys)
 {
     yang_stmt *ym;
+    cg_var    *cv;
 
     if ((ym = yang_find(ys, Y_CONFIG, NULL)) != NULL){
-        if (yang_cv_get(ym) == NULL) /* shouldnt happen */
+        if ((cv = yang_cv_get(ym)) == NULL) /* shouldnt happen */
             return 1;
-        return cv_bool_get(yang_cv_get(ym));
+        return cv_bool_get(cv);
     }
     return 1;
 }
@@ -4610,6 +4639,24 @@ yang_action_cb_add(yang_stmt *ys,
     return 0;
 }
 
+#ifdef OPTIMIZE_NO_PRESENCE_CONTAINER
+void *
+yang_nopresence_cache_get(yang_stmt *ys)
+{
+    return ys->ys_nopres_cache;
+}
+
+int
+yang_nopresence_cache_set(yang_stmt *ys,
+                          void      *x)
+{
+    if (ys->ys_nopres_cache)
+        xml_free(ys->ys_nopres_cache);
+    ys->ys_nopres_cache = x;
+    return 0;
+}
+#endif
+
 /*! Init yang code. Called before any yang code, before options
  *
  * Add two external tables for YANGs
diff --git a/lib/src/clixon_yang_internal.h b/lib/src/clixon_yang_internal.h
index 7e8b4080..2d812f36 100644
--- a/lib/src/clixon_yang_internal.h
+++ b/lib/src/clixon_yang_internal.h
@@ -114,7 +114,12 @@ struct yang_stmt {
         rpc_callback_t  *ysu_action_cb; /* Y_ACTION: Action callback list*/
         char            *ysu_filename;  /* Y_MODULE/Y_SUBMODULE: For debug/errors: filename */
         yang_type_cache *ysu_typecache; /* Y_TYPE: cache all typedef data except unions */
-
+#ifdef OPTIMIZE_YSPEC_NAMESPACE
+        map_str2ptr     *ysu_nscache;   /* Y_SPEC: namespace to module cache */
+#endif
+#ifdef OPTIMIZE_NO_PRESENCE_CONTAINER
+        cxobj           *ysu_nopres_cache; /* Y_CONTAINER: no-presence XML cache */
+#endif
     } u;
 };
 
@@ -122,5 +127,11 @@ struct yang_stmt {
 #define ys_action_cb      u.ysu_action_cb
 #define ys_filename       u.ysu_filename
 #define ys_typecache      u.ysu_typecache
+#ifdef OPTIMIZE_YSPEC_NAMESPACE
+#define ys_nscache        u.ysu_nscache
+#endif
+#ifdef OPTIMIZE_NO_PRESENCE_CONTAINER
+#define ys_nopres_cache   u.ysu_nopres_cache
+#endif
 
 #endif  /* _CLIXON_YANG_INTERNAL_H_ */
diff --git a/lib/src/clixon_yang_module.c b/lib/src/clixon_yang_module.c
index 9a3c8d6e..b2ed943f 100644
--- a/lib/src/clixon_yang_module.c
+++ b/lib/src/clixon_yang_module.c
@@ -609,6 +609,9 @@ yang_stmt *
 yang_find_module_by_namespace(yang_stmt *yspec,
                               char      *ns)
 {
+#ifdef OPTIMIZE_YSPEC_NAMESPACE
+    return yspec_nscache_get(yspec, ns);
+#else
     yang_stmt *ymod = NULL;
     int        inext;
 
@@ -621,6 +624,7 @@ yang_find_module_by_namespace(yang_stmt *yspec,
     }
  done:
     return ymod;
+#endif
 }
 
 /*! Given a yang spec, a namespace and revision, return yang module 
diff --git a/lib/src/clixon_yang_parse_lib.c b/lib/src/clixon_yang_parse_lib.c
index ee28ec56..a635c900 100644
--- a/lib/src/clixon_yang_parse_lib.c
+++ b/lib/src/clixon_yang_parse_lib.c
@@ -903,6 +903,9 @@ yang_parse_str(char         *str,
     /* Add filename for debugging and errors, see also ys_linenum on (each symbol?) */
     if (yang_filename_set(ymod, name) < 0)
         goto done;
+#ifdef OPTIMIZE_YSPEC_NAMESPACE
+    yspec_nscache_clear(yspec);
+#endif
  done:
     clixon_debug(CLIXON_DBG_PARSE, "retval:%p", ymod);
     ystack_pop(&yy);
@@ -2109,3 +2112,57 @@ ys_parse_sub(yang_stmt  *ys,
         free(extra);
     return retval;
 }
+
+#ifdef OPTIMIZE_YSPEC_NAMESPACE
+int
+yspec_nscache_clear(yang_stmt *yspec)
+{
+    if (yspec->ys_nscache){         /* Clear cache */
+        free(yspec->ys_nscache);
+        yspec->ys_nscache = NULL;
+    }
+    return 0;
+}
+
+/*!
+ */
+yang_stmt *
+yspec_nscache_get(yang_stmt *yspec,
+                  char      *ns)
+{
+    if (yspec->ys_nscache == NULL){
+        if (yspec_nscache_new(yspec) < 0)
+            return NULL;
+    }
+    return clixon_str2ptr(yspec->ys_nscache, ns, yang_len_get(yspec)+1);
+}
+
+/*!
+ */
+int
+yspec_nscache_new(yang_stmt *yspec)
+{
+    int          retval = -1;
+    map_str2ptr *mp;
+    yang_stmt   *ym;
+    int          i;
+
+    yspec_nscache_clear(yspec);
+    if ((yspec->ys_nscache = calloc(yang_len_get(yspec)+1, sizeof(*yspec->ys_nscache))) == NULL){
+        clixon_err(OE_UNIX, errno, "calloc");
+        goto done;
+    }
+    for (i=0; i<yang_len_get(yspec); i++){
+        ym = yang_child_i(yspec, i);
+        if (yang_keyword_get(ym) != Y_MODULE)
+            continue;
+        mp = &yspec->ys_nscache[i];
+        mp->mp_str = yang_find_mynamespace(ym);
+        mp->mp_ptr = ym;
+    }
+    clixon_str2ptr_sort(yspec->ys_nscache, yang_len_get(yspec)+1);
+    retval = 0;
+ done:
+    return retval;
+}
+#endif