diff --git a/configure.py b/configure.py
index 80841f95bf..6e094042aa 100755
--- a/configure.py
+++ b/configure.py
@@ -1694,6 +1694,7 @@ deps['test/boost/combined_tests'] += [
     'test/boost/group0_voter_calculator_test.cc',
     'test/boost/index_with_paging_test.cc',
     'test/boost/json_cql_query_test.cc',
+    'test/boost/large_data_guardrail_test.cc',
     'test/boost/large_paging_state_test.cc',
     'test/boost/loading_cache_test.cc',
     'test/boost/memtable_test.cc',
diff --git a/test/boost/CMakeLists.txt b/test/boost/CMakeLists.txt
index 8c42a09293..8df5178524 100644
--- a/test/boost/CMakeLists.txt
+++ b/test/boost/CMakeLists.txt
@@ -349,6 +349,7 @@ add_scylla_test(combined_tests
     group0_voter_calculator_test.cc
     index_with_paging_test.cc
     json_cql_query_test.cc
+    large_data_guardrail_test.cc
     large_paging_state_test.cc
     loading_cache_test.cc
     memtable_test.cc
diff --git a/test/boost/large_data_guardrail_test.cc b/test/boost/large_data_guardrail_test.cc
new file mode 100644
index 0000000000..d41d448deb
--- /dev/null
+++ b/test/boost/large_data_guardrail_test.cc
@@ -0,0 +1,233 @@
+/*
+ * Copyright (C) 2026-present ScyllaDB
+ */
+
+/*
+ * SPDX-License-Identifier: LicenseRef-ScyllaDB-Source-Available-1.1
+ */
+
+#include <boost/test/unit_test.hpp>
+#include <deque>
+#include "db/large_data_handler.hh"
+
+using sstables::large_data_record;
+using sstables::large_data_type;
+using db::lookup_key;
+using db::record_type;
+using db::record_compare;
+using db::record_set;
+
+namespace {
+
+large_data_record& make_record(std::deque<large_data_record>& store,
+        large_data_type type, bytes pk, bytes ck = {}, bytes col = {},
+        uint64_t value = 0, uint64_t elements_count = 0) {
+    store.emplace_back();
+    auto& rec = store.back();
+    rec.type = type;
+    rec.partition_key.value = std::move(pk);
+    rec.clustering_key.value = std::move(ck);
+    rec.column_name.value = std::move(col);
+    rec.value = value;
+    rec.elements_count = elements_count;
+    rec.range_tombstones = 0;
+    rec.dead_rows = 0;
+    return rec;
+}
+
+} // anonymous namespace
+
+BOOST_AUTO_TEST_SUITE(large_data_guardrail_test)
+
+BOOST_AUTO_TEST_CASE(test_partition_comparator_orders_by_pk_only) {
+    record_compare<record_type::partition> cmp;
+    std::deque<large_data_record> store;
+
+    auto& a = make_record(store, large_data_type::partition_size, to_bytes("aaa"));
+    auto& b = make_record(store, large_data_type::partition_size, to_bytes("bbb"));
+
+    BOOST_REQUIRE(cmp(a, b));
+    BOOST_REQUIRE(!cmp(b, a));
+    BOOST_REQUIRE(!cmp(a, a));
+
+    // Clustering key differences are ignored at partition level
+    auto& c = make_record(store, large_data_type::partition_size,
+            to_bytes("aaa"), to_bytes("zzz"));
+    BOOST_REQUIRE(!cmp(a, c));
+    BOOST_REQUIRE(!cmp(c, a));
+}
+
+BOOST_AUTO_TEST_CASE(test_row_comparator_orders_by_pk_then_ck) {
+    record_compare<record_type::row> cmp;
+    std::deque<large_data_record> store;
+
+    auto& a = make_record(store, large_data_type::row_size,
+            to_bytes("pk1"), to_bytes("ck_a"));
+    auto& b = make_record(store, large_data_type::row_size,
+            to_bytes("pk1"), to_bytes("ck_b"));
+    auto& c = make_record(store, large_data_type::row_size,
+            to_bytes("pk2"), to_bytes("ck_a"));
+
+    BOOST_REQUIRE(cmp(a, b));   // same pk, ck_a < ck_b
+    BOOST_REQUIRE(!cmp(b, a));
+    BOOST_REQUIRE(cmp(a, c));   // pk1 < pk2
+    BOOST_REQUIRE(cmp(b, c));   // pk1 < pk2 regardless of ck
+
+    // Column name differences are ignored at row level
+    auto& d = make_record(store, large_data_type::row_size,
+            to_bytes("pk1"), to_bytes("ck_a"), to_bytes("col_z"));
+    BOOST_REQUIRE(!cmp(a, d));
+    BOOST_REQUIRE(!cmp(d, a));
+}
+
+BOOST_AUTO_TEST_CASE(test_collection_comparator_orders_by_pk_ck_col) {
+    record_compare<record_type::collection> cmp;
+    std::deque<large_data_record> store;
+
+    auto& a = make_record(store, large_data_type::elements_in_collection,
+            to_bytes("pk1"), to_bytes("ck1"), to_bytes("col_a"));
+    auto& b = make_record(store, large_data_type::elements_in_collection,
+            to_bytes("pk1"), to_bytes("ck1"), to_bytes("col_b"));
+
+    BOOST_REQUIRE(cmp(a, b));
+    BOOST_REQUIRE(!cmp(b, a));
+    BOOST_REQUIRE(!cmp(a, a));
+
+    // Same pk+ck+col → equivalent
+    auto& c = make_record(store, large_data_type::elements_in_collection,
+            to_bytes("pk1"), to_bytes("ck1"), to_bytes("col_a"));
+    BOOST_REQUIRE(!cmp(a, c));
+    BOOST_REQUIRE(!cmp(c, a));
+}
+
+BOOST_AUTO_TEST_CASE(test_heterogeneous_lookup_with_lookup_key) {
+    record_compare<record_type::partition> cmp;
+    std::deque<large_data_record> store;
+
+    auto& rec = make_record(store, large_data_type::partition_size, to_bytes("pk1"));
+    auto pk = to_bytes("pk1");
+    lookup_key lk{bytes_view(pk), {}, {}};
+
+    // (record, key) and (key, record) must be consistent
+    BOOST_REQUIRE(!cmp(rec, lk));
+    BOOST_REQUIRE(!cmp(lk, rec));
+
+    auto pk2 = to_bytes("pk2");
+    lookup_key lk2{bytes_view(pk2), {}, {}};
+    BOOST_REQUIRE(cmp(rec, lk2));   // pk1 < pk2
+    BOOST_REQUIRE(!cmp(lk2, rec));  // pk2 > pk1
+}
+
+BOOST_AUTO_TEST_CASE(test_equal_range_groups_partition_records) {
+    record_set<record_type::partition> set;
+    std::deque<large_data_record> store;
+
+    auto& r1 = make_record(store, large_data_type::partition_size,
+            to_bytes("pk_a"), {}, {}, 100);
+    auto& r2 = make_record(store, large_data_type::partition_size,
+            to_bytes("pk_b"), {}, {}, 200);
+    auto& r3 = make_record(store, large_data_type::rows_in_partition,
+            to_bytes("pk_a"), {}, {}, 0, 50);
+    set.insert(r1);
+    set.insert(r2);
+    set.insert(r3);
+
+    // pk_a should match r1 (partition_size) and r3 (rows_in_partition)
+    auto pk_a = to_bytes("pk_a");
+    lookup_key lk{bytes_view(pk_a), {}, {}};
+    auto [begin, end] = set.equal_range(lk, set.key_comp());
+
+    uint64_t max_size = 0, max_rows = 0;
+    int count = 0;
+    for (auto it = begin; it != end; ++it) {
+        max_size = std::max(max_size, it->value);
+        max_rows = std::max(max_rows, it->elements_count);
+        ++count;
+    }
+    BOOST_REQUIRE_EQUAL(count, 2);
+    BOOST_REQUIRE_EQUAL(max_size, 100);
+    BOOST_REQUIRE_EQUAL(max_rows, 50);
+
+    // pk_c: no match
+    auto pk_c = to_bytes("pk_c");
+    lookup_key lk_miss{bytes_view(pk_c), {}, {}};
+    auto [b2, e2] = set.equal_range(lk_miss, set.key_comp());
+    BOOST_REQUIRE(b2 == e2);
+}
+
+BOOST_AUTO_TEST_CASE(test_equal_range_groups_row_records) {
+    record_set<record_type::row> set;
+    std::deque<large_data_record> store;
+
+    auto& r1 = make_record(store, large_data_type::row_size,
+            to_bytes("pk"), to_bytes("ck_a"), {}, 100);
+    auto& r2 = make_record(store, large_data_type::row_size,
+            to_bytes("pk"), to_bytes("ck_a"), {}, 300);
+    auto& r3 = make_record(store, large_data_type::row_size,
+            to_bytes("pk"), to_bytes("ck_b"), {}, 200);
+    set.insert(r1);
+    set.insert(r2);
+    set.insert(r3);
+
+    auto pk = to_bytes("pk");
+    auto ck_a = to_bytes("ck_a");
+    lookup_key lk{bytes_view(pk), bytes_view(ck_a), {}};
+    auto [begin, end] = set.equal_range(lk, set.key_comp());
+
+    uint64_t max_size = 0;
+    int count = 0;
+    for (auto it = begin; it != end; ++it) {
+        max_size = std::max(max_size, it->value);
+        ++count;
+    }
+    BOOST_REQUIRE_EQUAL(count, 2);  // r1 and r2
+    BOOST_REQUIRE_EQUAL(max_size, 300);
+}
+
+BOOST_AUTO_TEST_CASE(test_equal_range_groups_collection_records) {
+    record_set<record_type::collection> set;
+    std::deque<large_data_record> store;
+
+    auto& r1 = make_record(store, large_data_type::elements_in_collection,
+            to_bytes("pk"), to_bytes("ck"), to_bytes("col"), 0, 100);
+    auto& r2 = make_record(store, large_data_type::elements_in_collection,
+            to_bytes("pk"), to_bytes("ck"), to_bytes("col"), 0, 500);
+    auto& r3 = make_record(store, large_data_type::elements_in_collection,
+            to_bytes("pk"), to_bytes("ck"), to_bytes("other"), 0, 200);
+    set.insert(r1);
+    set.insert(r2);
+    set.insert(r3);
+
+    auto pk = to_bytes("pk");
+    auto ck = to_bytes("ck");
+    auto col = to_bytes("col");
+    lookup_key lk{bytes_view(pk), bytes_view(ck), bytes_view(col)};
+    auto [begin, end] = set.equal_range(lk, set.key_comp());
+
+    uint64_t max_count = 0;
+    int n = 0;
+    for (auto it = begin; it != end; ++it) {
+        max_count = std::max(max_count, it->elements_count);
+        ++n;
+    }
+    BOOST_REQUIRE_EQUAL(n, 2);  // r1 and r2
+    BOOST_REQUIRE_EQUAL(max_count, 500);
+}
+
+BOOST_AUTO_TEST_CASE(test_auto_unlink_on_record_destruction) {
+    record_set<record_type::partition> set;
+    {
+        std::deque<large_data_record> store;
+        auto& r1 = make_record(store, large_data_type::partition_size,
+                to_bytes("pk_a"), {}, {}, 100);
+        auto& r2 = make_record(store, large_data_type::partition_size,
+                to_bytes("pk_b"), {}, {}, 200);
+        set.insert(r1);
+        set.insert(r2);
+        BOOST_REQUIRE(!set.empty());
+    }
+    // store destroyed → records destroyed → auto_unlink fires
+    BOOST_REQUIRE(set.empty());
+}
+
+BOOST_AUTO_TEST_SUITE_END()