diff --git a/test/integration/double_buckets_test.lua b/test/integration/double_buckets_test.lua
new file mode 100644
index 00000000..2c3922cf
--- /dev/null
+++ b/test/integration/double_buckets_test.lua
@@ -0,0 +1,316 @@
+local t = require('luatest')
+local json = require('json')
+local fiber = require('fiber')
+
+local utils = require('crud.common.utils')
+
+local helpers = require('test.helper')
+
+local function wait_balance(g)
+    t.helpers.retrying({timeout=30}, function()
+        local buckets_count_s1 = g.cluster:server('s1-master').net_box:eval("return box.space._bucket:len()")
+        local buckets_count_s2 = g.cluster:server('s2-master').net_box:eval("return box.space._bucket:len()")
+        t.assert_equals(buckets_count_s1, 1500)
+        t.assert_equals(buckets_count_s2, 1500)
+    end)
+end
+
+local function balance_cluster(g)
+    if g.params.backend == "config" then
+        local cfg = g.cluster:cfg()
+        cfg.groups.storages.replicasets["s-1"].sharding = {
+            weight = 1,
+        }
+        cfg.groups.storages.replicasets["s-2"].sharding = {
+            weight = 1,
+        }
+        g.cluster:cfg(cfg)
+        wait_balance(g)
+    end
+end
+
+local pgroup_duplicates = t.group('double_buckets_duplicates', helpers.backend_matrix({
+    {engine = 'memtx', operation = 'replace'},
+    {engine = 'memtx', operation = 'insert'},
+    {engine = 'memtx', operation = 'upsert'},
+    {engine = 'memtx', operation = 'insert_many'},
+    {engine = 'memtx', operation = 'replace_many'},
+    {engine = 'memtx', operation = 'upsert_many'},
+}))
+
+pgroup_duplicates.before_all(function(g)
+    helpers.start_default_cluster(g, 'srv_simple_operations')
+end)
+
+pgroup_duplicates.after_all(function(g)
+    helpers.stop_cluster(g.cluster, g.params.backend)
+end)
+
+pgroup_duplicates.before_each(function(g)
+    helpers.truncate_space_on_cluster(g.cluster, 'customers')
+end)
+
+pgroup_duplicates.after_each(function(g)
+    balance_cluster(g)
+end)
+
+--- Rebalance stalls if we move all buckets at once; use a small subset.
+local test_tuples = {
+    {22, box.NULL, 'Alex', 34},
+    -- {92, box.NULL, 'Artur', 29},
+    -- {3, box.NULL, 'Anastasia', 22},
+    -- {5, box.NULL, 'Sergey', 25},
+    -- {9, box.NULL, 'Anna', 30},
+    -- {71, box.NULL, 'Oksana', 29},
+}
+
+local last_call = fiber.time()
+local duplicate_operations = {
+    insert = function(g)
+        return g.router:call('crud.insert', {'customers', {45, box.NULL, 'John Fedor', 42}})
+    end,
+    replace = function(g)
+        return g.router:call('crud.replace', {'customers', {45, box.NULL, 'John Fedor', 42}})
+    end,
+    upsert = function (g)
+        return g.router:call('crud.upsert', {'customers', {45, box.NULL, 'John Fedor', 42}, {{'+', 'age', 1}}})
+    end,
+    insert_many = function(g)
+        if fiber.time() - last_call < 1 then
+            return
+        end
+        last_call = fiber.time()
+        return g.router:call('crud.insert_many', {'customers', test_tuples})
+    end,
+    replace_many = function(g)
+        if fiber.time() - last_call < 1 then
+            return
+        end
+        last_call = fiber.time()
+        return g.router:call('crud.replace_many', {'customers', test_tuples})
+    end,
+    upsert_many = function(g)
+        if fiber.time() - last_call < 1 then
+            return
+        end
+        last_call = fiber.time()
+        local tuples = {}
+        for i = 1, 2 do
+            tuples[i] = {{i, box.NULL, 'John Fedor', 42}, {{'+', 'age', 1}}}
+        end
+        return g.router:call('crud.upsert_many', {'customers', tuples})
+    end
+}
+
+local function check_duplicates(tuples)
+    local ids = {}
+    for _, tuple in pairs(tuples) do
+        t.assert_equals(ids[tuple[1]], nil, ('duplicate to tuple: %s'):format(json.encode(tuple)))
+        ids[tuple[1]] = true
+    end
+end
+
+
+--- write requests cause duplicates by primary key in cluster
+pgroup_duplicates.test_duplicates = function(g)
+    t.skip_if(
+        not (
+            utils.tarantool_version_at_least(3, 1) and (g.params.backend == "config")
+        ),
+        'test implemented only for 3.1 and greater'
+    )
+    if g.params.backend == "config" then
+        t.xfail('not implemented yet')
+        duplicate_operations[g.params.operation](g)
+
+        local cfg = g.cluster:cfg()
+        cfg.groups.storages.replicasets["s-1"].sharding = {
+            weight = 0,
+        }
+        g.cluster:cfg(cfg)
+        t.helpers.retrying({timeout=30}, function()
+            local buckets_count = g.cluster:server('s1-master').net_box:eval("return box.space._bucket:len()")
+            duplicate_operations[g.params.operation](g)
+            t.assert_equals(buckets_count, 0)
+        end)
+
+        cfg.groups.storages.replicasets["s-2"].sharding = {
+            weight = 0,
+        }
+        cfg.groups.storages.replicasets["s-1"].sharding = {
+            weight = 1,
+        }
+        g.cluster:cfg(cfg)
+        t.helpers.retrying({timeout=30}, function()
+            local buckets_count = g.cluster:server('s2-master').net_box:eval("return box.space._bucket:len()")
+            duplicate_operations[g.params.operation](g)
+            t.assert_equals(buckets_count, 0)
+        end)
+
+        local res = g.router:call('crud.select', {'customers'})
+        check_duplicates(res.rows)
+    end
+end
+
+local pgroup_not_applied =  t.group('double_buckets_not_applied', helpers.backend_matrix({
+    {engine = 'memtx', operation = 'delete'},
+    {engine = 'memtx', operation = 'update'},
+    {engine = 'memtx', operation = 'get'},
+}))
+
+pgroup_not_applied.before_all(function(g)
+    helpers.start_default_cluster(g, 'srv_simple_operations')
+end)
+
+pgroup_not_applied.after_all(function(g)
+    helpers.stop_cluster(g.cluster, g.params.backend)
+end)
+
+pgroup_not_applied.before_each(function(g)
+    helpers.truncate_space_on_cluster(g.cluster, 'customers')
+end)
+
+pgroup_not_applied.after_each(function(g)
+    balance_cluster(g)
+end)
+
+local not_applied_operations = {
+    delete = {
+        call = function(g, key)
+            last_call = fiber.time()
+            return g.router:call('crud.delete', { 'customers', {key} })
+        end,
+        check_applied = function(rows, applied_ids)
+            for _, tuple in pairs(rows) do
+                t.assert_equals(
+                    applied_ids[tuple[1]],
+                    nil,
+                    ('tuples %s was marked as deleted, but exists'):format(json.encode(tuple))
+                )
+            end
+        end,
+        check_not_applied = function(not_applied_ids)
+            t.assert_equals(
+                next(not_applied_ids),
+                nil,
+                'tuples were inserted, but crud.delete returned 0 rows, as if there were no such tuples'
+            )
+        end
+    },
+    update = {
+        call = function(g, key)
+            return g.router:call('crud.update', { 'customers', key, {{'=', 'name', 'applied'}} })
+        end,
+        check_applied = function(rows, applied_ids)
+            for _, tuple in pairs(rows) do
+                if applied_ids[tuple[1]] then
+                    t.assert_equals(
+                        tuple[3],
+                        'applied',
+                        ('tuples %s was marked as updated, but was not updated'):format(json.encode(tuple))
+                    )
+                end
+            end
+        end,
+        check_not_applied = function(not_applied_ids)
+            t.assert_equals(
+                next(not_applied_ids),
+                nil,
+                'tuples were created, but crud.update returned 0 rows, as if there were no such tuples'
+            )
+        end
+    },
+    get = {
+        call = function (g, key)
+            return g.router:call('crud.get', { 'customers', key })
+        end,
+        check_applied = function() end,
+        check_not_applied = function(not_applied_ids)
+            t.assert_equals(
+                next(not_applied_ids),
+                nil,
+                'tuples were created, but crud.get returned 0 rows, as if there were no such tuples'
+            )
+        end
+    }
+}
+
+--- Some requests do not create duplicates but return 0 rows as if there is no tuple
+--- with this key. The tuple can still exist in cluster but be unavailable during
+--- rebalance. CRUD should return an error in this case, not 0 rows as if there were
+--- no tuples.
+pgroup_not_applied.test_not_applied = function(g)
+    t.skip_if(
+        not (
+            utils.tarantool_version_at_least(3, 1) and (g.params.backend == "config")
+        ),
+        'test implemented only for 3.1 and greater'
+    )
+    if g.params.backend == "config" then
+        t.xfail('not implemented yet')
+        local tuples, tuples_count = {}, 1000
+        for i = 1, tuples_count do
+            tuples[i] = {i, box.NULL, 'John Fedor', 42}
+        end
+
+        local _, err = g.router:call('crud.replace_many', {'customers', tuples})
+        t.assert_equals(err, nil)
+        local cfg = g.cluster:cfg()
+        cfg.groups.storages.replicasets["s-1"].sharding = {
+            weight = 0,
+        }
+        g.cluster:cfg(cfg)
+        local tuple_id = 1
+        local not_applied_ids = {}
+        local applied_ids = {}
+        t.helpers.retrying({timeout=30}, function()
+            if tuple_id > tuples_count then
+                return
+            end
+
+            local buckets_count = g.cluster:server('s1-master').net_box:eval("return box.space._bucket:len()")
+            local res, err = not_applied_operations[g.params.operation].call(g, tuple_id)
+            if err == nil then
+                if #res.rows == 0 then
+                    not_applied_ids[tuple_id] = true
+                else
+                    applied_ids[tuple_id] = true
+                end
+                tuple_id = tuple_id + 1
+            end
+
+            t.assert_equals(buckets_count, 0)
+        end)
+
+        cfg.groups.storages.replicasets["s-2"].sharding = {
+            weight = 0,
+        }
+        cfg.groups.storages.replicasets["s-1"].sharding = {
+            weight = 1,
+        }
+        g.cluster:cfg(cfg)
+        t.helpers.retrying({timeout=30}, function()
+            if tuple_id > tuples_count then
+                return
+            end
+
+            local buckets_count = g.cluster:server('s2-master').net_box:eval("return box.space._bucket:len()")
+            local res, err = not_applied_operations[g.params.operation].call(g, tuple_id)
+
+            if err == nil then
+                if #res.rows == 0 then
+                    not_applied_ids[tuple_id] = true
+                else
+                    applied_ids[tuple_id] = true
+                end
+                tuple_id = tuple_id + 1
+            end
+
+            t.assert_equals(buckets_count, 0)
+        end)
+
+        local res = g.router:call('crud.select', {'customers'})
+        not_applied_operations[g.params.operation].check_applied(res.rows, applied_ids)
+        not_applied_operations[g.params.operation].check_not_applied(not_applied_ids)
+    end
+end
diff --git a/test/tarantool3_helpers/cluster.lua b/test/tarantool3_helpers/cluster.lua
index 21574d2b..df8caf81 100644
--- a/test/tarantool3_helpers/cluster.lua
+++ b/test/tarantool3_helpers/cluster.lua
@@ -297,34 +297,7 @@ function Cluster:cfg(new_config)
     return table.deepcopy(self.config)
 end
 
-local function strip_all_entries(t, name)
-    if type(t) ~= 'table' then
-        return t
-    end
-
-    t[name] = nil
-
-    for k, v in pairs(t) do
-        t[k] = strip_all_entries(v, name)
-    end
-
-    return t
-end
-
-local function check_only_roles_cfg_changed_in_groups(old_groups, new_groups)
-    old_groups = table.deepcopy(old_groups)
-    new_groups = table.deepcopy(new_groups)
-
-    local old_groups_no_roles_cfg = strip_all_entries(old_groups, 'roles_cfg')
-    local new_groups_no_roles_cfg = strip_all_entries(new_groups, 'roles_cfg')
-
-    t.assert_equals(new_groups_no_roles_cfg, old_groups_no_roles_cfg,
-                    'groups reload supports only roles_cfg reload')
-end
-
 function Cluster:reload_config(new_config)
-    check_only_roles_cfg_changed_in_groups(self.config.groups, new_config.groups)
-
     for _, server in ipairs(self.servers) do
         write_config(self.dirs[server], new_config)
     end