diff --git a/CCDB/include/CCDB/CcdbApi.h b/CCDB/include/CCDB/CcdbApi.h
index ea396a5b49402..9ba8869fb7de3 100644
--- a/CCDB/include/CCDB/CcdbApi.h
+++ b/CCDB/include/CCDB/CcdbApi.h
@@ -392,6 +392,9 @@ class CcdbApi //: public DatabaseInterface
   // Loads files from alien and cvmfs into given destination.
   bool loadLocalContentToMemory(o2::pmr::vector<char>& dest, std::string& url) const;
 
+  // add annotated flattened headers in the end of the blob
+  static void appendFlatHeader(o2::pmr::vector<char>& dest, const std::map<std::string, std::string>& headers);
+
   // the failure to load the file to memory is signaled by 0 size and non-0 capacity
   static bool isMemoryFileInvalid(const o2::pmr::vector<char>& v) { return v.size() == 0 && v.capacity() > 0; }
   template <typename T>
@@ -610,6 +613,16 @@ class CcdbApi //: public DatabaseInterface
     return getSnapshotDir(topdir, path) + '/' + sfile;
   }
 
+  template <typename MAP> // can be either std::map or std::multimap
+  static size_t getFlatHeaderSize(const MAP& Headers)
+  {
+    size_t hsize = sizeof(int) + sizeof(FlatHeaderAnnot); // annotation size
+    for (auto& h : Headers) {
+      hsize += h.first.length() + h.second.length() + 2; // 2*(string_buffer + terminating null character)
+    }
+    return hsize;
+  }
+
   // tmp helper and single point of entry for a CURL perform call
   // helps to switch between easy handle perform and multi handles in a single place
   CURLcode CURL_perform(CURL* handle) const;
@@ -632,6 +645,8 @@ class CcdbApi //: public DatabaseInterface
   size_t mCurlTimeoutDownload = 15; // download timeout in seconds, can be configured via ALICEO2_CCDB_CURL_TIMEOUT_DOWNLOAD, updated according to the deployment mode
   size_t mCurlTimeoutUpload = 15;   // upload timeout in seconds, can be configured via ALICEO2_CCDB_CURL_TIMEOUT_UPLOAD, updated according to the deployment mode
 
+  static constexpr char FlatHeaderAnnot[] = "$HEADER$"; // annotation for flat header
+
   ClassDefNV(CcdbApi, 1);
 };
 
diff --git a/CCDB/src/CcdbApi.cxx b/CCDB/src/CcdbApi.cxx
index a17458a33e5e6..3b622b87e7e7b 100644
--- a/CCDB/src/CcdbApi.cxx
+++ b/CCDB/src/CcdbApi.cxx
@@ -1687,12 +1687,15 @@ void CcdbApi::scheduleDownload(RequestContext& requestContext, size_t* requestCo
     ho.counter++;
     try {
       if (chunk.capacity() < chunk.size() + realsize) {
+        // estimate headers size when converted to annotated text string
+        const char hannot[] = "header";
+        size_t hsize = getFlatHeaderSize(ho.header);
         auto cl = ho.header.find("Content-Length");
         if (cl != ho.header.end()) {
           size_t sizeFromHeader = std::stol(cl->second);
-          sz = std::max(chunk.size() * (sizeFromHeader ? 1 : 2) + realsize, sizeFromHeader);
+          sz = hsize + std::max(chunk.size() * (sizeFromHeader ? 1 : 2) + realsize, sizeFromHeader);
         } else {
-          sz = std::max(chunk.size() * 2, chunk.size() + realsize);
+          sz = hsize + std::max(chunk.size() * 2, chunk.size() + realsize);
           // LOGP(debug, "SIZE IS NOT IN HEADER, allocate {}", sz);
         }
         chunk.reserve(sz);
@@ -1885,6 +1888,25 @@ void CcdbApi::loadFileToMemory(o2::pmr::vector<char>& dest, std::string const& p
   vectoredLoadFileToMemory(contexts);
 }
 
+void CcdbApi::appendFlatHeader(o2::pmr::vector<char>& dest, const std::map<std::string, std::string>& headers)
+{
+  size_t hsize = getFlatHeaderSize(headers), cnt = dest.size();
+  dest.resize(cnt + hsize);
+  auto addString = [&dest, &cnt](const std::string& s) {
+    for (char c : s) {
+      dest[cnt++] = c;
+    }
+    dest[cnt++] = 0;
+  };
+
+  for (auto& h : headers) {
+    addString(h.first);
+    addString(h.second);
+  }
+  *reinterpret_cast<int*>(&dest[cnt]) = hsize;                                     // store size
+  std::memcpy(&dest[cnt + sizeof(int)], FlatHeaderAnnot, sizeof(FlatHeaderAnnot)); // annotate the flattened headers map
+}
+
 void CcdbApi::navigateSourcesAndLoadFile(RequestContext& requestContext, int& fromSnapshot, size_t* requestCounter) const
 {
   LOGP(debug, "loadFileToMemory {} ETag=[{}]", requestContext.path, requestContext.etag);
diff --git a/Framework/CCDBSupport/src/CCDBHelpers.cxx b/Framework/CCDBSupport/src/CCDBHelpers.cxx
index 6c510ad189ac5..ab1a21e263eb0 100644
--- a/Framework/CCDBSupport/src/CCDBHelpers.cxx
+++ b/Framework/CCDBSupport/src/CCDBHelpers.cxx
@@ -260,6 +260,7 @@ auto populateCacheWith(std::shared_ptr<CCDBFetcherHelper> const& helper,
         helper->mapURL2UUID[path].cacheMiss++;
         helper->mapURL2UUID[path].minSize = std::min(v.size(), helper->mapURL2UUID[path].minSize);
         helper->mapURL2UUID[path].maxSize = std::max(v.size(), helper->mapURL2UUID[path].maxSize);
+        api.appendFlatHeader(v, headers);
         auto cacheId = allocator.adoptContainer(output, std::move(v), DataAllocator::CacheStrategy::Always, header::gSerializationMethodCCDB);
         helper->mapURL2DPLCache[path] = cacheId;
         O2_SIGNPOST_EVENT_EMIT(ccdb, sid, "populateCacheWith", "Caching %{public}s for %{public}s (DPL id %" PRIu64 ")", path.data(), headers["ETag"].data(), cacheId.value);
@@ -273,6 +274,7 @@ auto populateCacheWith(std::shared_ptr<CCDBFetcherHelper> const& helper,
         helper->mapURL2UUID[path].cacheMiss++;
         helper->mapURL2UUID[path].minSize = std::min(v.size(), helper->mapURL2UUID[path].minSize);
         helper->mapURL2UUID[path].maxSize = std::max(v.size(), helper->mapURL2UUID[path].maxSize);
+        api.appendFlatHeader(v, headers);
         auto cacheId = allocator.adoptContainer(output, std::move(v), DataAllocator::CacheStrategy::Always, header::gSerializationMethodCCDB);
         helper->mapURL2DPLCache[path] = cacheId;
         O2_SIGNPOST_EVENT_EMIT(ccdb, sid, "populateCacheWith", "Caching %{public}s for %{public}s (DPL id %" PRIu64 ")", path.data(), headers["ETag"].data(), cacheId.value);
@@ -395,6 +397,7 @@ AlgorithmSpec CCDBHelpers::fetchFromCCDB()
               helper->mapURL2UUID[path].minSize = std::min(v.size(), helper->mapURL2UUID[path].minSize);
               helper->mapURL2UUID[path].maxSize = std::max(v.size(), helper->mapURL2UUID[path].maxSize);
               newOrbitResetTime = getOrbitResetTime(v);
+              api.appendFlatHeader(v, headers);
               auto cacheId = allocator.adoptContainer(output, std::move(v), DataAllocator::CacheStrategy::Always, header::gSerializationMethodNone);
               helper->mapURL2DPLCache[path] = cacheId;
               O2_SIGNPOST_EVENT_EMIT(ccdb, sid, "fetchFromCCDB", "Caching %{public}s for %{public}s (DPL id %" PRIu64 ")", path.data(), headers["ETag"].data(), cacheId.value);
@@ -405,6 +408,7 @@ AlgorithmSpec CCDBHelpers::fetchFromCCDB()
               helper->mapURL2UUID[path].minSize = std::min(v.size(), helper->mapURL2UUID[path].minSize);
               helper->mapURL2UUID[path].maxSize = std::max(v.size(), helper->mapURL2UUID[path].maxSize);
               newOrbitResetTime = getOrbitResetTime(v);
+              api.appendFlatHeader(v, headers);
               auto cacheId = allocator.adoptContainer(output, std::move(v), DataAllocator::CacheStrategy::Always, header::gSerializationMethodNone);
               helper->mapURL2DPLCache[path] = cacheId;
               O2_SIGNPOST_EVENT_EMIT(ccdb, sid, "fetchFromCCDB", "Caching %{public}s for %{public}s (DPL id %" PRIu64 ")", path.data(), headers["ETag"].data(), cacheId.value);
diff --git a/Framework/Core/include/Framework/DataRefUtils.h b/Framework/Core/include/Framework/DataRefUtils.h
index 264533def326d..c63b06357b8ed 100644
--- a/Framework/Core/include/Framework/DataRefUtils.h
+++ b/Framework/Core/include/Framework/DataRefUtils.h
@@ -179,6 +179,7 @@ struct DataRefUtils {
   }
   // Decode a CCDB object using the CcdbApi.
   static void* decodeCCDB(DataRef const& ref, std::type_info const& info);
+  static std::map<std::string, std::string> extractCCDBHeaders(DataRef const& ref);
 
   static o2::header::DataHeader::PayloadSizeType getPayloadSize(const DataRef& ref)
   {
diff --git a/Framework/Core/src/DataRefUtils.cxx b/Framework/Core/src/DataRefUtils.cxx
index 239aba95aa3ce..b32c47387e69a 100644
--- a/Framework/Core/src/DataRefUtils.cxx
+++ b/Framework/Core/src/DataRefUtils.cxx
@@ -10,6 +10,7 @@
 // or submit itself to any jurisdiction.
 
 #include <typeinfo>
+#include <cstring>
 #include "Framework/DataRefUtils.h"
 #include "Framework/RuntimeError.h"
 #include "Framework/Logger.h"
@@ -80,11 +81,29 @@ void* DataRefUtils::decodeCCDB(DataRef const& ref, std::type_info const& tinfo)
   Int_t previousErrorLevel = gErrorIgnoreLevel;
   gErrorIgnoreLevel = kFatal;
   auto* dh = o2::header::get<o2::header::DataHeader*>(ref.header);
-  TMemFile memFile("name", const_cast<char*>(ref.payload), dh->payloadSize, "READ");
+  const char* buff = const_cast<char*>(ref.payload);
+  size_t flSize = dh->payloadSize;
+  // does it have a flattened headers map attached in the end?
+  constexpr char FlatHeaderAnnot[] = "$HEADER$";
+  constexpr int Offset = sizeof(int) + sizeof(FlatHeaderAnnot);
+  int headerSize = 0;
+  LOGP(debug, "DHPayloadSize={}>{} Ref:{}/{} Cmp {}:{}", dh->payloadSize, Offset, dh->dataOrigin.as<std::string>(), dh->dataDescription.as<std::string>(), std::string{buff + dh->payloadSize - sizeof(FlatHeaderAnnot)}, std::string{FlatHeaderAnnot});
+
+  if (dh->payloadSize >= Offset &&
+      !std::strncmp(buff + dh->payloadSize - sizeof(FlatHeaderAnnot), FlatHeaderAnnot, sizeof(FlatHeaderAnnot))) {
+    headerSize = *reinterpret_cast<const int*>(buff + dh->payloadSize - Offset);
+  }
+  if (headerSize <= 0) {
+    LOGP(fatal, "Anomalous flattened header size {} extracted", headerSize);
+  }
+  TMemFile memFile("name", const_cast<char*>(ref.payload), dh->payloadSize - headerSize, "READ");
   gErrorIgnoreLevel = previousErrorLevel;
   if (memFile.IsZombie()) {
     return nullptr;
   }
+
+  extractCCDBHeaders(ref);
+
   TClass* tcl = TClass::GetClass(tinfo);
   result = extractFromTFile(memFile, tcl, "ccdb_object");
   if (!result) {
@@ -94,4 +113,36 @@ void* DataRefUtils::decodeCCDB(DataRef const& ref, std::type_info const& tinfo)
   return result;
 }
 
+std::map<std::string, std::string> DataRefUtils::extractCCDBHeaders(DataRef const& ref)
+{
+  auto* dh = o2::header::get<o2::header::DataHeader*>(ref.header);
+  const char* buff = const_cast<char*>(ref.payload);
+  // does it have a flattened headers map attached in the end?
+  constexpr char FlatHeaderAnnot[] = "$HEADER$";
+  constexpr int Offset = sizeof(int) + sizeof(FlatHeaderAnnot);
+  int headerSize = 0, ss0 = 0;
+  if (dh->payloadSize >= Offset && !std::strncmp(buff + dh->payloadSize - sizeof(FlatHeaderAnnot), FlatHeaderAnnot, sizeof(FlatHeaderAnnot))) {
+    headerSize = *reinterpret_cast<const int*>(buff + dh->payloadSize - Offset);
+  }
+  if (headerSize <= 0) {
+    LOGP(fatal, "Anomalous flattened header size {} extracted", headerSize);
+  }
+  buff += dh->payloadSize - headerSize; // jump to the start of flattened header
+  headerSize -= Offset;
+  const char* str0 = &buff[ss0++];
+  std::map<std::string, std::string> res;
+  while (ss0 < headerSize) {
+    if (buff[ss0++] == 0) {
+      if (!str0) {
+        str0 = &buff[ss0]; // new key string is found
+      } else {
+        res.emplace(std::string(str0), std::string(&buff[ss0])); // new value string found, add key value to the map
+        LOGP(debug, "Header{} {}:{}", res.size(), std::string(str0), std::string(&buff[ss0]));
+        str0 = nullptr;
+      }
+    }
+  }
+  return res;
+}
+
 } // namespace o2::framework