diff --git a/Framework/Core/include/Framework/DataModelViews.h b/Framework/Core/include/Framework/DataModelViews.h
index b7a334454bb6e..f42ef85ec78e1 100644
--- a/Framework/Core/include/Framework/DataModelViews.h
+++ b/Framework/Core/include/Framework/DataModelViews.h
@@ -206,15 +206,10 @@ struct get_num_payloads {
 
 struct MessageSet;
 
-struct MessageStore {
-  std::span<MessageSet> sets;
-  size_t inputsPerSlot = 0;
-};
-
 struct inputs_for_slot {
   TimesliceSlot slot;
   template <typename R>
-    requires requires(R r) { std::ranges::random_access_range<decltype(r.sets)>; }
+    requires requires(R r) { requires std::ranges::random_access_range<decltype(r.sets)>; }
   friend std::span<o2::framework::MessageSet> operator|(R&& r, inputs_for_slot self)
   {
     return std::span(r.sets[self.slot.index * r.inputsPerSlot]);
diff --git a/Framework/Core/include/Framework/MessageSet.h b/Framework/Core/include/Framework/MessageSet.h
index e7ae70e0ea2e5..281f9c42a0773 100644
--- a/Framework/Core/include/Framework/MessageSet.h
+++ b/Framework/Core/include/Framework/MessageSet.h
@@ -12,13 +12,13 @@
 #define FRAMEWORK_MESSAGESET_H
 
 #include "Framework/PartRef.h"
+#include <fairmq/Message.h>
+#include "Framework/DataModelViews.h"
 #include <memory>
 #include <vector>
 #include <cassert>
 
-namespace o2
-{
-namespace framework
+namespace o2::framework
 {
 
 /// A set of inflight messages.
@@ -83,21 +83,21 @@ struct MessageSet {
   }
 
   /// get number of in-flight O2 messages
-  size_t size() const
+  [[nodiscard]] size_t size() const
   {
-    return messageMap.size();
+    return messages | count_parts{};
   }
 
   /// get number of header-payload pairs
-  size_t getNumberOfPairs() const
+  [[nodiscard]] size_t getNumberOfPairs() const
   {
-    return pairMap.size();
+    return messages | count_payloads{};
   }
 
   /// get number of payloads for an in-flight message
-  size_t getNumberOfPayloads(size_t mi) const
+  [[nodiscard]] size_t getNumberOfPayloads(size_t mi) const
   {
-    return messageMap[mi].size;
+    return messages | get_num_payloads{mi};
   }
 
   /// clear the set
@@ -179,6 +179,6 @@ struct MessageSet {
   }
 };
 
-} // namespace framework
-} // namespace o2
+} // namespace o2::framework
+
 #endif // FRAMEWORK_MESSAGESET_H
diff --git a/Framework/Core/test/test_MessageSet.cxx b/Framework/Core/test/test_MessageSet.cxx
index d56e32fea1adb..37f823197ef18 100644
--- a/Framework/Core/test/test_MessageSet.cxx
+++ b/Framework/Core/test/test_MessageSet.cxx
@@ -10,126 +10,164 @@
 // or submit itself to any jurisdiction.
 
 #include <fairmq/Message.h>
+#include <fairmq/TransportFactory.h>
 #include "Framework/MessageSet.h"
+#include "Framework/DataProcessingHeader.h"
+#include "Headers/Stack.h"
+#include "MemoryResources/MemoryResources.h"
 #include <catch_amalgamated.hpp>
 
 using namespace o2::framework;
 
-TEST_CASE("MessageSet") {
+TEST_CASE("MessageSet")
+{
   o2::framework::MessageSet msgSet;
-  std::vector<fair::mq::MessagePtr> ptrs;
-  std::unique_ptr<fair::mq::Message> msg(nullptr);
+  o2::header::DataHeader dh{};
+  dh.splitPayloadParts = 0;
+  dh.splitPayloadIndex = 0;
+  o2::framework::DataProcessingHeader dph{0, 1};
+  auto transport = fair::mq::TransportFactory::CreateTransportFactory("zeromq");
+  fair::mq::MessagePtr payload(transport->CreateMessage());
+  auto channelAlloc = o2::pmr::getTransportAllocator(transport.get());
+  fair::mq::MessagePtr header = o2::pmr::getMessage(o2::header::Stack{channelAlloc, dh, dph});
   std::unique_ptr<fair::mq::Message> msg2(nullptr);
-  ptrs.emplace_back(std::move(msg));
+  std::vector<fair::mq::MessagePtr> ptrs;
+  ptrs.emplace_back(std::move(header));
   ptrs.emplace_back(std::move(msg2));
   msgSet.add([&ptrs](size_t i) -> fair::mq::MessagePtr& { return ptrs[i]; }, 2);
 
   REQUIRE(msgSet.messages.size() == 2);
-  REQUIRE(msgSet.messageMap.size() == 1);
-  REQUIRE(msgSet.pairMap.size() == 1);
-  REQUIRE(msgSet.messageMap[0].position == 0);
-  REQUIRE(msgSet.messageMap[0].size == 1);
-
-  REQUIRE(msgSet.pairMap[0].partIndex == 0);
-  REQUIRE(msgSet.pairMap[0].payloadIndex == 0);
+  REQUIRE((msgSet.messages | count_payloads{}) == 1);
+  REQUIRE((msgSet.messages | get_dataref_indices{0, 0}).headerIdx == 0);
+  REQUIRE((msgSet.messages | get_dataref_indices{0, 0}).payloadIdx == 1);
+  REQUIRE((msgSet.messages | get_pair{0}).headerIdx == 0);
+  REQUIRE((msgSet.messages | get_pair{0}).payloadIdx == 1);
+  CHECK_THROWS((msgSet.messages | get_pair{1}));
 }
 
-TEST_CASE("MessageSetWithFunction") {
+TEST_CASE("MessageSetWithFunction")
+{
   std::vector<fair::mq::MessagePtr> ptrs;
-  std::unique_ptr<fair::mq::Message> msg(nullptr);
+  o2::header::DataHeader dh{};
+  dh.splitPayloadParts = 0;
+  dh.splitPayloadIndex = 0;
+  o2::framework::DataProcessingHeader dph{0, 1};
+  auto transport = fair::mq::TransportFactory::CreateTransportFactory("zeromq");
+  fair::mq::MessagePtr payload(transport->CreateMessage());
+  auto channelAlloc = o2::pmr::getTransportAllocator(transport.get());
+  fair::mq::MessagePtr header = o2::pmr::getMessage(o2::header::Stack{channelAlloc, dh, dph});
   std::unique_ptr<fair::mq::Message> msg2(nullptr);
-  ptrs.emplace_back(std::move(msg));
+  ptrs.emplace_back(std::move(header));
   ptrs.emplace_back(std::move(msg2));
   o2::framework::MessageSet msgSet([&ptrs](size_t i) -> fair::mq::MessagePtr& { return ptrs[i]; }, 2);
 
   REQUIRE(msgSet.messages.size() == 2);
-  REQUIRE(msgSet.messageMap.size() == 1);
-  REQUIRE(msgSet.pairMap.size() == 1);
-  REQUIRE(msgSet.messageMap[0].position == 0);
-  REQUIRE(msgSet.messageMap[0].size == 1);
-
-  REQUIRE(msgSet.pairMap[0].partIndex == 0);
-  REQUIRE(msgSet.pairMap[0].payloadIndex == 0);
+  REQUIRE((msgSet.messages | count_payloads{}) == 1);
+  REQUIRE((msgSet.messages | get_dataref_indices{0, 0}).headerIdx == 0);
+  REQUIRE((msgSet.messages | get_dataref_indices{0, 0}).payloadIdx == 1);
+  REQUIRE((msgSet.messages | get_pair{0}).headerIdx == 0);
+  REQUIRE((msgSet.messages | get_pair{0}).payloadIdx == 1);
+  CHECK_THROWS((msgSet.messages | get_pair{1}));
 }
 
-TEST_CASE("MessageSetWithMultipart") {
+TEST_CASE("MessageSetWithMultipart")
+{
   std::vector<fair::mq::MessagePtr> ptrs;
-  std::unique_ptr<fair::mq::Message> msg(nullptr);
+  o2::header::DataHeader dh{};
+  dh.splitPayloadParts = 2;
+  dh.splitPayloadIndex = 2;
+  o2::framework::DataProcessingHeader dph{0, 1};
+  auto transport = fair::mq::TransportFactory::CreateTransportFactory("zeromq");
+  fair::mq::MessagePtr payload(transport->CreateMessage());
+  auto channelAlloc = o2::pmr::getTransportAllocator(transport.get());
+  fair::mq::MessagePtr header = o2::pmr::getMessage(o2::header::Stack{channelAlloc, dh, dph});
   std::unique_ptr<fair::mq::Message> msg2(nullptr);
   std::unique_ptr<fair::mq::Message> msg3(nullptr);
-  ptrs.emplace_back(std::move(msg));
+  ptrs.emplace_back(std::move(header));
   ptrs.emplace_back(std::move(msg2));
   ptrs.emplace_back(std::move(msg3));
   o2::framework::MessageSet msgSet([&ptrs](size_t i) -> fair::mq::MessagePtr& { return ptrs[i]; }, 3);
 
   REQUIRE(msgSet.messages.size() == 3);
-  REQUIRE(msgSet.messageMap.size() == 1);
-  REQUIRE(msgSet.pairMap.size() == 2);
-  REQUIRE(msgSet.messageMap[0].position == 0);
-  REQUIRE(msgSet.messageMap[0].size == 2);
-
-  REQUIRE(msgSet.pairMap[0].partIndex == 0);
-  REQUIRE(msgSet.pairMap[0].payloadIndex == 0);
-  REQUIRE(msgSet.pairMap[1].partIndex == 0);
-  REQUIRE(msgSet.pairMap[1].payloadIndex == 1);
+  REQUIRE((msgSet.messages | count_payloads{}) == 2);
+  REQUIRE((msgSet.messages | get_dataref_indices{0, 0}).headerIdx == 0);
+  REQUIRE((msgSet.messages | get_dataref_indices{0, 0}).payloadIdx == 1);
+  REQUIRE((msgSet.messages | get_dataref_indices{0, 1}).headerIdx == 0);
+  REQUIRE((msgSet.messages | get_dataref_indices{0, 1}).payloadIdx == 2);
+  REQUIRE((msgSet.messages | get_pair{0}).headerIdx == 0);
+  REQUIRE((msgSet.messages | get_pair{0}).payloadIdx == 1);
+  REQUIRE((msgSet.messages | get_pair{1}).headerIdx == 0);
+  REQUIRE((msgSet.messages | get_pair{1}).payloadIdx == 2);
+  CHECK_THROWS((msgSet.messages | get_pair{2}));
 }
 
-TEST_CASE("MessageSetAddPartRef") {
+TEST_CASE("MessageSetAddPartRef")
+{
   std::vector<fair::mq::MessagePtr> ptrs;
   std::unique_ptr<fair::mq::Message> msg(nullptr);
   std::unique_ptr<fair::mq::Message> msg2(nullptr);
   ptrs.emplace_back(std::move(msg));
   ptrs.emplace_back(std::move(msg2));
-  PartRef ref {std::move(msg), std::move(msg2)};
+  PartRef ref{std::move(msg), std::move(msg2)};
   o2::framework::MessageSet msgSet;
   msgSet.add(std::move(ref));
 
   REQUIRE(msgSet.messages.size() == 2);
-  REQUIRE(msgSet.messageMap.size() == 1);
-  REQUIRE(msgSet.pairMap.size() == 1);
-  REQUIRE(msgSet.messageMap[0].position == 0);
-  REQUIRE(msgSet.messageMap[0].size == 1);
-
-  REQUIRE(msgSet.pairMap[0].partIndex == 0);
-  REQUIRE(msgSet.pairMap[0].payloadIndex == 0);
 }
 
 TEST_CASE("MessageSetAddMultiple")
 {
   std::vector<fair::mq::MessagePtr> ptrs;
-  std::unique_ptr<fair::mq::Message> msg(nullptr);
+  o2::header::DataHeader dh1{};
+  dh1.splitPayloadParts = 0;
+  dh1.splitPayloadIndex = 0;
+  o2::header::DataHeader dh2{};
+  dh2.splitPayloadParts = 1;
+  dh2.splitPayloadIndex = 0;
+  o2::header::DataHeader dh3{};
+  dh3.splitPayloadParts = 2;
+  dh3.splitPayloadIndex = 2;
+  o2::framework::DataProcessingHeader dph{0, 1};
+  auto transport = fair::mq::TransportFactory::CreateTransportFactory("zeromq");
+  fair::mq::MessagePtr payload(transport->CreateMessage());
+  auto channelAlloc = o2::pmr::getTransportAllocator(transport.get());
+  fair::mq::MessagePtr header1 = o2::pmr::getMessage(o2::header::Stack{channelAlloc, dh1, dph});
+  fair::mq::MessagePtr header2 = o2::pmr::getMessage(o2::header::Stack{channelAlloc, dh2, dph});
+  fair::mq::MessagePtr header3 = o2::pmr::getMessage(o2::header::Stack{channelAlloc, dh3, dph});
+
   std::unique_ptr<fair::mq::Message> msg2(nullptr);
-  ptrs.emplace_back(std::move(msg));
-  ptrs.emplace_back(std::move(msg2));
-  PartRef ref{std::move(msg), std::move(msg2)};
+  std::unique_ptr<fair::mq::Message> msg3(nullptr);
+  PartRef ref{std::move(header1), std::move(msg2)};
   o2::framework::MessageSet msgSet;
   msgSet.add(std::move(ref));
-  PartRef ref2{std::move(msg), std::move(msg2)};
+  PartRef ref2{std::move(header2), std::move(msg2)};
   msgSet.add(std::move(ref2));
   std::vector<fair::mq::MessagePtr> msgs;
-  msgs.push_back(std::unique_ptr<fair::mq::Message>(nullptr));
+  msgs.push_back(std::move(header3));
   msgs.push_back(std::unique_ptr<fair::mq::Message>(nullptr));
   msgs.push_back(std::unique_ptr<fair::mq::Message>(nullptr));
   msgSet.add([&msgs](size_t i) {
     return std::move(msgs[i]);
-  }, 3);
+  },
+             3);
 
   REQUIRE(msgSet.messages.size() == 7);
-  REQUIRE(msgSet.messageMap.size() == 3);
-  REQUIRE(msgSet.pairMap.size() == 4);
-  REQUIRE(msgSet.messageMap[0].position == 0);
-  REQUIRE(msgSet.messageMap[0].size == 1);
-  REQUIRE(msgSet.messageMap[1].position == 2);
-  REQUIRE(msgSet.messageMap[1].size == 1);
-  REQUIRE(msgSet.messageMap[2].position == 4);
-  REQUIRE(msgSet.messageMap[2].size == 2);
 
-  REQUIRE(msgSet.pairMap[0].partIndex == 0);
-  REQUIRE(msgSet.pairMap[0].payloadIndex == 0);
-  REQUIRE(msgSet.pairMap[1].partIndex == 1);
-  REQUIRE(msgSet.pairMap[1].payloadIndex == 0);
-  REQUIRE(msgSet.pairMap[2].partIndex == 2);
-  REQUIRE(msgSet.pairMap[2].payloadIndex == 0);
-  REQUIRE(msgSet.pairMap[3].partIndex == 2);
-  REQUIRE(msgSet.pairMap[3].payloadIndex == 1);
+  REQUIRE((msgSet.messages | count_payloads{}) == 4);
+  REQUIRE((msgSet.messages | get_dataref_indices{0, 0}).headerIdx == 0);
+  REQUIRE((msgSet.messages | get_dataref_indices{0, 0}).payloadIdx == 1);
+  REQUIRE((msgSet.messages | get_dataref_indices{1, 0}).headerIdx == 2);
+  REQUIRE((msgSet.messages | get_dataref_indices{1, 0}).payloadIdx == 3);
+  REQUIRE((msgSet.messages | get_dataref_indices{2, 0}).headerIdx == 4);
+  REQUIRE((msgSet.messages | get_dataref_indices{2, 0}).payloadIdx == 5);
+  REQUIRE((msgSet.messages | get_dataref_indices{2, 1}).headerIdx == 4);
+  REQUIRE((msgSet.messages | get_dataref_indices{2, 1}).payloadIdx == 6);
+  REQUIRE((msgSet.messages | get_pair{0}).headerIdx == 0);
+  REQUIRE((msgSet.messages | get_pair{0}).payloadIdx == 1);
+  REQUIRE((msgSet.messages | get_pair{1}).headerIdx == 2);
+  REQUIRE((msgSet.messages | get_pair{1}).payloadIdx == 3);
+  REQUIRE((msgSet.messages | get_pair{2}).headerIdx == 4);
+  REQUIRE((msgSet.messages | get_pair{2}).payloadIdx == 5);
+  REQUIRE((msgSet.messages | get_pair{3}).headerIdx == 4);
+  REQUIRE((msgSet.messages | get_pair{3}).payloadIdx == 6);
 }