diff --git a/include/opendht/node_cache.h b/include/opendht/node_cache.h
index e5f90868..97e62cd1 100644
--- a/include/opendht/node_cache.h
+++ b/include/opendht/node_cache.h
@@ -26,9 +26,9 @@
 namespace dht {
 
 struct NodeCache {
-    std::shared_ptr<Node> getNode(const InfoHash& id, sa_family_t family);
-    std::shared_ptr<Node> getNode(const InfoHash& id, const SockAddr&, time_point now, bool confirmed, bool client=false);
-    std::vector<std::shared_ptr<Node>> getCachedNodes(const InfoHash& id, sa_family_t sa_f, size_t count);
+    Sp<Node> getNode(const InfoHash& id, sa_family_t family);
+    Sp<Node> getNode(const InfoHash& id, const SockAddr&, time_point now, bool confirmed, bool client=false);
+    std::vector<Sp<Node>> getCachedNodes(const InfoHash& id, sa_family_t sa_f, size_t count) const;
 
     /**
      * Reset the connectivity state of every node,
@@ -40,11 +40,12 @@ struct NodeCache {
 private:
     class NodeMap : public std::map<InfoHash, std::weak_ptr<Node>> {
     public:
-        std::shared_ptr<Node> getNode(const InfoHash& id);
-        std::shared_ptr<Node> getNode(const InfoHash& id, const SockAddr&, time_point now, bool confirmed, bool client);
+        Sp<Node> getNode(const InfoHash& id);
+        Sp<Node> getNode(const InfoHash& id, const SockAddr&, time_point now, bool confirmed, bool client);
         void clearBadNodes();
     };
 
+    const NodeMap& cache(sa_family_t af) const { return af == AF_INET ? cache_4 : cache_6; }
     NodeMap& cache(sa_family_t af) { return af == AF_INET ? cache_4 : cache_6; }
     NodeMap cache_4;
     NodeMap cache_6;
diff --git a/src/node_cache.cpp b/src/node_cache.cpp
index 65a1cd07..f821b29b 100644
--- a/src/node_cache.cpp
+++ b/src/node_cache.cpp
@@ -20,41 +20,44 @@
 
 namespace dht {
 
-std::shared_ptr<Node>
+Sp<Node>
 NodeCache::getNode(const InfoHash& id, sa_family_t family) {
     return cache(family).getNode(id);
 }
 
-std::shared_ptr<Node>
+Sp<Node>
 NodeCache::getNode(const InfoHash& id, const SockAddr& addr, time_point now, bool confirm, bool client) {
     if (id == zeroes)
         return std::make_shared<Node>(id, addr);
     return cache(addr.getFamily()).getNode(id, addr, now, confirm, client);
 }
 
-std::vector<std::shared_ptr<Node>>
-NodeCache::getCachedNodes(const InfoHash& id, sa_family_t sa_f, size_t count) {
+std::vector<Sp<Node>>
+NodeCache::getCachedNodes(const InfoHash& id, sa_family_t sa_f, size_t count) const
+{
     const auto& c = cache(sa_f);
-    auto it_p = c.lower_bound(id),
-         it_n = it_p;
 
-    std::vector<std::shared_ptr<Node>> nodes;
+    std::vector<Sp<Node>> nodes;
     nodes.reserve(std::min(c.size(), count));
     NodeMap::const_iterator it;
+    auto dec_it = [&c](NodeMap::const_iterator& it) {
+        auto ret = it;
+        it = (it == c.cbegin()) ? c.cend() : std::prev(it);
+        return ret;
+    };
 
-    if (it_p != c.begin()) /* Create 2 separate iterator if we could */
-        --it_p;
+    auto it_p = c.lower_bound(id),
+        it_n = it_p;
+    if (it_p != c.cend())
+        dec_it(it_p); /* Create 2 separate iterator if we could */
 
-    while (nodes.size() < count and (it_n != c.end() or it_p != c.end())) {
+    while (nodes.size() < count and (it_n != c.cend() or it_p != c.cend())) {
         /* If one of the iterator is at the end, then take the other one
            If they are both in middle of somewhere comapre both and take
            the closest to the id. */
-        if (it_p == c.end())       it = it_n++;
-        else if (it_n == c.end())  it = it_p--;
-        else                       it = id.xorCmp(it_p->first, it_n->first) < 0 ? it_p-- : it_n++;
-
-        if (it == c.begin())
-            it_p = c.end();
+        if (it_p == c.cend())       it = it_n++;
+        else if (it_n == c.cend())  it = dec_it(it_p);
+        else                        it = id.xorCmp(it_p->first, it_n->first) < 0 ? dec_it(it_p) : it_n++;
 
         if (auto n = it->second.lock())
             if ( not n->isExpired() and not n->isClient() )
@@ -75,7 +78,7 @@ NodeCache::clearBadNodes(sa_family_t family)
     }
 }
 
-std::shared_ptr<Node>
+Sp<Node>
 NodeCache::NodeMap::getNode(const InfoHash& id)
 {
     auto wn = find(id);
@@ -87,7 +90,7 @@ NodeCache::NodeMap::getNode(const InfoHash& id)
     return {};
 }
 
-std::shared_ptr<Node>
+Sp<Node>
 NodeCache::NodeMap::getNode(const InfoHash& id, const SockAddr& addr, time_point now, bool confirm, bool client)
 {
     auto it = emplace(id, std::weak_ptr<Node>{});