diff --git a/conanfile.py b/conanfile.py
index 0cb18bd1d..ca96905c5 100644
--- a/conanfile.py
+++ b/conanfile.py
@@ -9,7 +9,7 @@
 
 class HomestoreConan(ConanFile):
     name = "homestore"
-    version = "6.5.5"
+    version = "6.5.6"
 
     homepage = "https://github.com/eBay/Homestore"
     description = "HomeStore Storage Engine"
diff --git a/src/include/homestore/index/index_internal.hpp b/src/include/homestore/index/index_internal.hpp
index 85c2a304d..fea20dbd6 100644
--- a/src/include/homestore/index/index_internal.hpp
+++ b/src/include/homestore/index/index_internal.hpp
@@ -97,7 +97,8 @@ struct IndexBuffer : public sisl::ObjLifeCounter< IndexBuffer > {
     sisl::atomic_counter< int > m_wait_for_down_buffers{0}; // Number of children need to wait for before persisting
 #ifndef NDEBUG
     // Down buffers are not mandatory members, but only to keep track of any bugs and asserts
-    std::vector< std::weak_ptr< IndexBuffer > > m_down_buffers;
+    std::vector<std::weak_ptr<IndexBuffer> > m_down_buffers;
+    std::mutex m_down_buffers_mtx;
     std::shared_ptr< IndexBuffer > m_prev_up_buffer; // Keep a copy for debugging
 #endif
 
@@ -123,6 +124,13 @@ struct IndexBuffer : public sisl::ObjLifeCounter< IndexBuffer > {
 
     std::string to_string() const;
     std::string to_string_dot() const;
+
+    void add_down_buffer(const IndexBufferPtr &buf);
+
+    void remove_down_buffer(const IndexBufferPtr &buf);
+#ifndef NDEBUG
+    bool is_in_down_buffers(const IndexBufferPtr &buf);
+#endif
 };
 
 // This is a special buffer which is used to write to the meta block
diff --git a/src/lib/index/index_cp.cpp b/src/lib/index/index_cp.cpp
index d58e33c22..578fae997 100644
--- a/src/lib/index/index_cp.cpp
+++ b/src/lib/index/index_cp.cpp
@@ -266,33 +266,16 @@ void IndexCPContext::process_txn_record(txn_record const* rec, std::map< BlkId,
 #ifndef NDEBUG
             //  if (!is_sibling_link || (buf->m_up_buffer == real_up_buf)) { return buf;}
             //  Already linked with same buf or its not a sibling link to override
-            bool found{false};
-            for (auto const& dbuf : real_up_buf->m_down_buffers) {
-                if (dbuf.lock() == buf) {
-                    found = true;
-                    break;
-                }
+            if (real_up_buf->is_in_down_buffers(buf)) {
+                return buf;
             }
-            if (found) { return buf; }
-            real_up_buf->m_down_buffers.emplace_back(buf);
 #endif
 
             if (buf->m_up_buffer != real_up_buf) {
                 if (buf->m_up_buffer) {
-                    buf->m_up_buffer->m_wait_for_down_buffers.decrement(1);
-#ifndef NDEBUG
-                    bool found{false};
-                    for (auto it = buf->m_up_buffer->m_down_buffers.begin(); it != buf->m_up_buffer->m_down_buffers.end(); ++it) {
-                        if (it->lock() == buf) {
-                            buf->m_up_buffer->m_down_buffers.erase(it);
-                            found = true;
-                            break;
-                        }
-                    }
-                    HS_DBG_ASSERT(found, "Down buffer is linked to Up buf, but up_buf doesn't have down_buf in its list");
-#endif
+                    buf->m_up_buffer->remove_down_buffer(buf);
                 }
-                real_up_buf->m_wait_for_down_buffers.increment(1);
+                real_up_buf->add_down_buffer(buf);
                 buf->m_up_buffer = real_up_buf;
             }
         }
diff --git a/src/lib/index/index_service.cpp b/src/lib/index/index_service.cpp
index 4b3fb5d11..49755a4ef 100644
--- a/src/lib/index/index_service.cpp
+++ b/src/lib/index/index_service.cpp
@@ -162,9 +162,12 @@ std::string IndexBuffer::to_string() const {
         // store m_down_buffers in a string
         std::string down_bufs = "";
 #ifndef NDEBUG
-        for (auto const& down_buf : m_down_buffers) {
-            if (auto ptr = down_buf.lock()) {
-                fmt::format_to(std::back_inserter(down_bufs), "[{}]", voidptr_cast(ptr.get()));
+        {
+            std::lock_guard lg(m_down_buffers_mtx);
+            for (auto const &down_buf: m_down_buffers) {
+                if (auto ptr = down_buf.lock()) {
+                    fmt::format_to(std::back_inserter(down_bufs), "[{}]", voidptr_cast(ptr.get()));
+                }
             }
         }
 #endif
@@ -178,6 +181,7 @@ std::string IndexBuffer::to_string() const {
                            down_bufs);
     }
 }
+
 std::string IndexBuffer::to_string_dot() const {
     auto str = fmt::format("IndexBuffer {} ", reinterpret_cast< void* >(const_cast< IndexBuffer* >(this)));
     if (m_bytes == nullptr) {
@@ -190,6 +194,45 @@ std::string IndexBuffer::to_string_dot() const {
     return str;
 }
 
+void IndexBuffer::add_down_buffer(const IndexBufferPtr &buf) {
+    m_wait_for_down_buffers.increment();
+#ifndef NDEBUG
+    {
+        std::lock_guard lg(m_down_buffers_mtx);
+        m_down_buffers.push_back(buf);
+    }
+#endif
+}
+
+void IndexBuffer::remove_down_buffer(const IndexBufferPtr &buf) {
+    m_wait_for_down_buffers.decrement();
+#ifndef NDEBUG
+    bool found{false}; {
+        std::lock_guard lg(m_down_buffers_mtx);
+        for (auto it = buf->m_up_buffer->m_down_buffers.begin(); it != buf->m_up_buffer->m_down_buffers.end(); ++it) {
+            if (it->lock() == buf) {
+                buf->m_up_buffer->m_down_buffers.erase(it);
+                found = true;
+                break;
+            }
+        }
+    }
+    HS_DBG_ASSERT(found, "Down buffer is linked to up_buf, but up_buf doesn't have down_buf in its list");
+#endif
+}
+
+#ifndef NDEBUG
+bool IndexBuffer::is_in_down_buffers(const IndexBufferPtr &buf) {
+    std::lock_guard<std::mutex> lg(m_down_buffers_mtx);
+    for (auto const &dbuf: m_down_buffers) {
+        if (dbuf.lock() == buf) {
+            return true;
+        }
+    }
+    return false;
+}
+#endif
+
 MetaIndexBuffer::MetaIndexBuffer(superblk< index_table_sb >& sb) : IndexBuffer{nullptr, BlkId{}}, m_sb{sb} {
     m_is_meta_buf = true;
 }
diff --git a/src/lib/index/wb_cache.cpp b/src/lib/index/wb_cache.cpp
index b17d67dc8..04383d8ac 100644
--- a/src/lib/index/wb_cache.cpp
+++ b/src/lib/index/wb_cache.cpp
@@ -396,14 +396,8 @@ void IndexWBCache::link_buf(IndexBufferPtr const& up_buf, IndexBufferPtr const&
             HS_DBG_ASSERT((real_up_buf->m_dirtied_cp_id == down_buf->m_dirtied_cp_id) || (real_up_buf->is_meta_buf()),
                           "Up buffer is not modified by current cp, but down buffer is linked to it");
 #ifndef NDEBUG
-            bool found{false};
-            for (auto const& dbuf : real_up_buf->m_down_buffers) {
-                if (dbuf.lock() == down_buf) {
-                    found = true;
-                    break;
-                }
-            }
-            HS_DBG_ASSERT(found, "Down buffer is linked to Up buf, but up_buf doesn't have down_buf in its list");
+            HS_DBG_ASSERT(real_up_buf->is_in_down_buffers(down_buf),
+                          "Down buffer is linked to Up buf, but up_buf doesn't have down_buf in its list");
 #endif
             return;
         }
@@ -412,25 +406,10 @@ void IndexWBCache::link_buf(IndexBufferPtr const& up_buf, IndexBufferPtr const&
     // Now we link the down_buffer to the real up_buffer
     if (down_buf->m_up_buffer) {
         // release existing up_buffer's wait count
-        down_buf->m_up_buffer->m_wait_for_down_buffers.decrement();
-#ifndef NDEBUG
-        bool found{false};
-        for (auto it = down_buf->m_up_buffer->m_down_buffers.begin(); it != down_buf->m_up_buffer->m_down_buffers.end();
-             ++it) {
-            if (it->lock() == down_buf) {
-                down_buf->m_up_buffer->m_down_buffers.erase(it);
-                found = true;
-                break;
-            }
-        }
-        HS_DBG_ASSERT(found, "Down buffer is linked to Up buf, but up_buf doesn't have down_buf in its list");
-#endif
+        down_buf->m_up_buffer->remove_down_buffer(down_buf);
     }
-    real_up_buf->m_wait_for_down_buffers.increment(1);
     down_buf->m_up_buffer = real_up_buf;
-#ifndef NDEBUG
-    real_up_buf->m_down_buffers.emplace_back(down_buf);
-#endif
+    real_up_buf->add_down_buffer(down_buf);
 }
 
 void IndexWBCache::free_buf(const IndexBufferPtr& buf, CPContext* cp_ctx) {
@@ -535,21 +514,8 @@ void IndexWBCache::recover(sisl::byte_view sb) {
                 pending_bufs.push_back(buf->m_up_buffer);
             } else {
                 // Just ignore it
-                buf->m_up_buffer->m_wait_for_down_buffers.decrement();
-#ifndef NDEBUG
-                bool found{false};
-                for (auto it = buf->m_up_buffer->m_down_buffers.begin();
-                     it != buf->m_up_buffer->m_down_buffers.end(); ++it) {
-                    auto sp = it->lock();
-                    if (sp && sp == buf) {
-                        found = true;
-                        buf->m_up_buffer->m_down_buffers.erase(it);
-                        break;
-                    }
-                }
-                HS_DBG_ASSERT(found,
-                              "Down buffer is linked to Up buf, but up_buf doesn't have down_buf in its list");
-#endif
+                buf->m_up_buffer->remove_down_buffer(buf);
+                buf->m_up_buffer = nullptr;
             }
         }
     }
@@ -754,7 +720,10 @@ std::pair< IndexBufferPtr, bool > IndexWBCache::on_buf_flush_done_internal(Index
                                                                            IndexBufferPtr const& buf) {
     IndexBufferPtrList buf_list;
 #ifndef NDEBUG
-    buf->m_down_buffers.clear();
+    {
+        std::lock_guard lg(buf->m_down_buffers_mtx);
+        buf->m_down_buffers.clear();
+    }
 #endif
     buf->set_state(index_buf_state_t::CLEAN);