diff --git a/ConflictSet.cpp b/ConflictSet.cpp
index 16fa1c0..f81681a 100644
--- a/ConflictSet.cpp
+++ b/ConflictSet.cpp
@@ -21,6 +21,33 @@
 
 // ==================== BEGIN IMPLEMENTATION ====================
 
+int compare(std::span<const uint8_t> lhs, std::span<const uint8_t> rhs) {
+  int cl = std::min<int>(lhs.size(), rhs.size());
+  int c = cl == 0 ? 0 : memcmp(lhs.data(), rhs.data(), cl);
+  if (c != 0) {
+    return c;
+  }
+  return int(rhs.size()) - int(lhs.size());
+}
+
+std::span<uint8_t> strincMutate(std::span<uint8_t> str, bool &ok) {
+  int index;
+  for (index = str.size() - 1; index >= 0; index--)
+    if (str[index] != 255)
+      break;
+
+  // Must not be called with a string that consists only of zero or more '\xff'
+  // bytes.
+  if (index < 0) {
+    ok = false;
+    return {};
+  }
+  ok = true;
+  str = str.subspan(0, index + 1);
+  ++str.back();
+  return str;
+}
+
 struct Entry {
   int64_t pointVersion;
   int64_t rangeVersion;
@@ -485,6 +512,26 @@ Node *nextPhysical(Node *node) {
   }
 }
 
+Node *nextPhysical(Node *node, Vector<uint8_t> &searchPath) {
+  int index = -1;
+  for (;;) {
+    auto nextChild = getChildGeq(node, index + 1);
+    if (nextChild >= 0) {
+      auto *result = getChildExists(node, nextChild);
+      searchPath.push_back(nextChild);
+      searchPath.insert(searchPath.end(), result->partialKey,
+                        result->partialKey + result->partialKeyLen);
+      return result;
+    }
+    if (node->parent == nullptr) {
+      return nullptr;
+    }
+    searchPath.resize(int(searchPath.size()) - 1 - node->partialKeyLen);
+    index = node->parentsIndex;
+    node = node->parent;
+  }
+}
+
 Node *nextLogical(Node *node) {
   for (node = nextPhysical(node); node != nullptr && !node->entryPresent;
        node = nextPhysical(node))
@@ -511,6 +558,27 @@ Node *nextSibling(Node *node) {
   }
 }
 
+Node *nextSibling(Node *node, Vector<uint8_t> &searchPath) {
+  for (;;) {
+    if (node->parent == nullptr) {
+      assert(searchPath.size() == 0);
+      return nullptr;
+    }
+    auto next = getChildGeq(node->parent, node->parentsIndex + 1);
+    if (next < 0) {
+      node = node->parent;
+      searchPath.resize(int(searchPath.size()) - 1 - node->partialKeyLen);
+    } else {
+      searchPath.resize(int(searchPath.size()) - 1 - node->partialKeyLen);
+      auto *result = getChildExists(node->parent, next);
+      searchPath.push_back(next);
+      searchPath.insert(searchPath.end(), result->partialKey,
+                        result->partialKey + result->partialKeyLen);
+      return result;
+    }
+  }
+}
+
 struct FirstGeqStepwise {
   Node *n;
   std::span<const uint8_t> remaining;
@@ -691,6 +759,23 @@ namespace {
 std::string getSearchPathPrintable(Node *n);
 }
 
+Vector<uint8_t> getSearchPath(Arena &arena, Node *n) {
+  assert(n != nullptr);
+  auto result = vector<uint8_t>(arena);
+  for (;;) {
+    for (int i = n->partialKeyLen - 1; i >= 0; --i) {
+      result.push_back(n->partialKey[i]);
+    }
+    if (n->parent == nullptr) {
+      break;
+    }
+    result.push_back(n->parentsIndex);
+    n = n->parent;
+  }
+  std::reverse(result.begin(), result.end());
+  return result;
+}
+
 bool checkRangeRead(Node *n, const std::span<const uint8_t> begin,
                     const std::span<const uint8_t> end, int64_t readVersion) {
   auto left = FirstGeqStepwise{n, begin};
@@ -725,26 +810,6 @@ bool checkRangeRead(Node *n, const std::span<const uint8_t> begin,
       ;
   }
 
-  Arena arena{64 << 10};
-  // auto leftBorder = hashSet<Node *>(arena);
-  // auto rightBorder = hashSet<Node *>(arena);
-  auto leftBorder = vector<Node *>(arena);
-  auto rightBorder = vector<Node *>(arena);
-  {
-    auto *l = left.n;
-    auto *r = right.n;
-    for (; l != nullptr && r != nullptr; l = l->parent, r = r->parent) {
-      leftBorder.push_back(l);
-      rightBorder.push_back(r);
-    }
-    for (; l != nullptr; l = l->parent) {
-      leftBorder.push_back(l);
-    }
-    for (; r != nullptr; r = r->parent) {
-      rightBorder.push_back(r);
-    }
-  }
-
 #if DEBUG_VERBOSE && !defined(NDEBUG)
   fprintf(stderr, "firstGeq for `%s' got `%s'\n", printable(begin).c_str(),
           getSearchPathPrintable(left.n).c_str());
@@ -764,31 +829,30 @@ bool checkRangeRead(Node *n, const std::span<const uint8_t> begin,
     return false;
   }
 
-  // TODO better data structure for pointer set. Also collect during first
-  // traversal?
-  for (auto *iter = nextPhysical(left.n); iter != right.n;) {
-    // const bool onLeftPath = leftBorder.find(iter) != leftBorder.end();
-    // const bool onRightPath = rightBorder.find(iter) != rightBorder.end();
-    const bool onLeftPath = std::find(leftBorder.begin(), leftBorder.end(),
-                                      iter) != leftBorder.end();
-    const bool onRightPath = std::find(rightBorder.begin(), rightBorder.end(),
-                                       iter) != rightBorder.end();
-    if (!onLeftPath && !onRightPath) {
+  Arena arena;
+  auto searchPath = getSearchPath(arena, left.n);
+
+  for (auto *iter = nextPhysical(left.n, searchPath); iter != right.n;) {
+    assert(searchPath == getSearchPath(arena, iter));
+    bool ok = true;
+    auto rangeEnd = strincMutate(searchPath, ok);
+    if (!ok) {
+      return iter->maxVersion <= readVersion;
+    }
+    int c = compare(rangeEnd, end);
+    --rangeEnd.back();
+    if (c == 0) {
+      return iter->maxVersion <= readVersion;
+    } else if (c < 0) {
       if (iter->maxVersion > readVersion) {
         return false;
       }
-      // Skip subtree
-      iter = nextSibling(iter);
+      iter = nextSibling(iter, searchPath);
     } else {
-      if (onRightPath && iter->maxVersion <= readVersion) {
+      if (iter->maxVersion <= readVersion) {
         return true;
       }
-      if (iter->entryPresent &&
-          std::max(iter->entry.pointVersion, iter->entry.rangeVersion) >
-              readVersion) {
-        return false;
-      }
-      iter = nextPhysical(iter);
+      iter = nextPhysical(iter, searchPath);
     }
   }
   return true;
@@ -1113,18 +1177,7 @@ std::string strinc(std::string_view str, bool &ok) {
 std::string getSearchPath(Node *n) {
   assert(n != nullptr);
   Arena arena;
-  auto result = vector<char>(arena);
-  for (;;) {
-    for (int i = n->partialKeyLen - 1; i >= 0; --i) {
-      result.push_back(n->partialKey[i]);
-    }
-    if (n->parent == nullptr) {
-      break;
-    }
-    result.push_back(n->parentsIndex);
-    n = n->parent;
-  }
-  std::reverse(result.begin(), result.end());
+  auto result = getSearchPath(arena, n);
   return std::string((const char *)result.data(), result.size());
 }