diff --git a/src/replica/replica_stub.cpp b/src/replica/replica_stub.cpp
index 6b21ba83fd..070f843f21 100644
--- a/src/replica/replica_stub.cpp
+++ b/src/replica/replica_stub.cpp
@@ -488,7 +488,7 @@ std::vector<replica_stub::disk_replicas_info> replica_stub::get_all_disk_dirs()
 void replica_stub::load_replica(dir_node *dn,
                                 const std::string &replica_dir,
                                 utils::ex_lock &reps_lock,
-                                replicas &reps)
+                                replica_map_by_gpid &reps)
 {
     LOG_INFO("loading replica: tag={}, replica_dir={}", dn->tag, replica_dir);
 
@@ -518,14 +518,16 @@ void replica_stub::load_replica(dir_node *dn,
     utils::auto_lock<utils::ex_lock> l(reps_lock);
     const auto rep_iter = reps.find(rep->get_gpid());
     CHECK(rep_iter == reps.end(),
-          "conflict replica dir: {} <--> {}",
+          "{}@{}: newly loaded dir {} conflicts with existing {} while loading replica",
+          rep->get_gpid(),
+          dsn_primary_host_port(),
           rep->dir(),
           rep_iter->second->dir());
 
     reps.emplace(rep->get_gpid(), rep);
 }
 
-void replica_stub::load_replicas(replicas &reps)
+void replica_stub::load_replicas(replica_map_by_gpid &reps)
 {
     const auto &disks = get_all_disk_dirs();
 
@@ -615,8 +617,10 @@ void replica_stub::load_replicas(replicas &reps)
                     // Ensure that the thread pool is non-partitioned.
                     LPC_REPLICATION_INIT_LOAD,
                     &_tracker,
-                    std::bind(static_cast<void (replica_stub::*)(
-                                  dir_node *, const std::string &, utils::ex_lock &, replicas &)>(
+                    std::bind(static_cast<void (replica_stub::*)(dir_node *,
+                                                                 const std::string &,
+                                                                 utils::ex_lock &,
+                                                                 replica_map_by_gpid &)>(
                                   &replica_stub::load_replica),
                               this,
                               dn,
@@ -729,7 +733,7 @@ void replica_stub::initialize(const replication_options &opts, bool clear /* = f
     // Start to load replicas in available data directories.
     LOG_INFO("start to load replicas");
 
-    replicas reps;
+    replica_map_by_gpid reps;
 
     utils::chronograph chrono;
     load_replicas(reps);
@@ -894,7 +898,7 @@ dsn::error_code replica_stub::on_kill_replica(gpid id)
 {
     LOG_INFO("kill replica: gpid = {}", id);
     if (id.get_app_id() == -1 || id.get_partition_index() == -1) {
-        replicas rs;
+        replica_map_by_gpid rs;
         {
             zauto_read_lock l(_replicas_lock);
             rs = _replicas;
@@ -1521,7 +1525,7 @@ void replica_stub::on_node_query_reply(error_code err,
                  resp.partitions.size(),
                  resp.gc_replicas.size());
 
-        replicas reps;
+        replica_map_by_gpid reps;
         {
             zauto_read_lock rl(_replicas_lock);
             reps = _replicas;
@@ -1671,7 +1675,7 @@ void replica_stub::on_meta_server_disconnected()
 
     _state = NS_Disconnected;
 
-    replicas reps;
+    replica_map_by_gpid reps;
     {
         zauto_read_lock rl(_replicas_lock);
         reps = _replicas;
@@ -2064,7 +2068,7 @@ void replica_stub::open_replica(
         METRIC_VAR_DECREMENT(opening_replicas);
 
         CHECK(_replicas.find(id) == _replicas.end(), "replica {} is already in _replicas", id);
-        _replicas.insert(replicas::value_type(rep->get_gpid(), rep));
+        _replicas.insert(replica_map_by_gpid::value_type(rep->get_gpid(), rep));
         METRIC_VAR_INCREMENT(total_replicas);
 
         _closed_replicas.erase(id);
@@ -2645,14 +2649,14 @@ replica_stub::exec_command_on_replica(const std::vector<std::string> &args,
         return std::string("invalid arguments");
     }
 
-    replicas rs;
+    replica_map_by_gpid rs;
     {
         zauto_read_lock l(_replicas_lock);
         rs = _replicas;
     }
 
     std::set<gpid> required_ids;
-    replicas choosed_rs;
+    replica_map_by_gpid choosed_rs;
     if (!args.empty()) {
         for (int i = 0; i < args.size(); i++) {
             std::vector<std::string> arg_strs;
@@ -2915,7 +2919,7 @@ replica_ptr replica_stub::create_child_replica_if_not_found(gpid child_pid,
             CHECK_NOTNULL(dn, "");
             auto *rep = new replica(this, child_pid, *app, dn, false);
             rep->_config.status = partition_status::PS_INACTIVE;
-            _replicas.insert(replicas::value_type(child_pid, rep));
+            _replicas.insert(replica_map_by_gpid::value_type(child_pid, rep));
             LOG_INFO("mock create_child_replica_if_not_found succeed");
             return rep;
         });
@@ -2934,7 +2938,7 @@ replica_ptr replica_stub::create_child_replica_if_not_found(gpid child_pid,
         } else {
             replica *rep = new_replica(child_pid, *app, false, false, parent_dir);
             if (rep != nullptr) {
-                auto pr = _replicas.insert(replicas::value_type(child_pid, rep));
+                auto pr = _replicas.insert(replica_map_by_gpid::value_type(child_pid, rep));
                 CHECK(pr.second, "child replica {} has been existed", rep->name());
                 METRIC_VAR_INCREMENT(total_replicas);
                 _closed_replicas.erase(child_pid);
diff --git a/src/replica/replica_stub.h b/src/replica/replica_stub.h
index dc6ac4074e..c0bb7f43b6 100644
--- a/src/replica/replica_stub.h
+++ b/src/replica/replica_stub.h
@@ -27,7 +27,6 @@
 #pragma once
 
 #include <gtest/gtest_prod.h>
-#include <algorithm>
 #include <atomic>
 #include <cstdint>
 #include <functional>
@@ -122,11 +121,10 @@ class test_checker;
 }
 class cold_backup_context;
 class replica_split_manager;
-typedef std::function<void(const ::dsn::host_port & /*from*/,
-                           const replica_configuration & /*new_config*/,
-                           bool /*is_closing*/)>
-    replica_state_subscriber;
-typedef std::unordered_map<gpid, replica_ptr> replicas;
+
+using replica_state_subscriber = std::function<void(const ::dsn::host_port & /*from*/,
+                                                    const replica_configuration & /*new_config*/,
+                                                    bool /*is_closing*/)>;
 
 class replica_stub;
 
@@ -397,15 +395,17 @@ class replica_stub : public serverlet<replica_stub>, public ref_counter
     // directory for a replica.
     virtual replica_ptr load_replica(dir_node *dn, const std::string &replica_dir);
 
+    using replica_map_by_gpid = std::unordered_map<gpid, replica_ptr>;
+
     // The same as the above `load_replica` function, except that this function is to load
     // each replica to `reps` with protection from `reps_lock`.
     void load_replica(dir_node *dn,
                       const std::string &replica_dir,
                       utils::ex_lock &reps_lock,
-                      replicas &reps);
+                      replica_map_by_gpid &reps);
 
     // Load all replicas simultaneously from all disks to `reps`.
-    void load_replicas(replicas &reps);
+    void load_replicas(replica_map_by_gpid &reps);
 
     // Clean up the memory state and on disk data if creating replica failed.
     void clear_on_failure(replica *rep);
@@ -497,17 +497,19 @@ class replica_stub : public serverlet<replica_stub>, public ref_counter
     FRIEND_TEST(replica_test, test_auto_trash_of_corruption);
     FRIEND_TEST(replica_test, test_clear_on_failure);
 
-    typedef std::unordered_map<gpid, ::dsn::task_ptr> opening_replicas;
-    typedef std::unordered_map<gpid, std::tuple<task_ptr, replica_ptr, app_info, replica_info>>
-        closing_replicas; // <gpid, <close_task, replica, app_info, replica_info> >
-    typedef std::map<gpid, std::pair<app_info, replica_info>>
-        closed_replicas; // <gpid, <app_info, replica_info> >
+    using opening_replica_map_by_gpid = std::unordered_map<gpid, task_ptr>;
+
+    // `task_ptr` is the task being closed.
+    using closing_replica_map_by_gpid =
+        std::unordered_map<gpid, std::tuple<task_ptr, replica_ptr, app_info, replica_info>>;
+
+    using closed_replica_map_by_gpid = std::map<gpid, std::pair<app_info, replica_info>>;
 
     mutable zrwlock_nr _replicas_lock;
-    replicas _replicas;
-    opening_replicas _opening_replicas;
-    closing_replicas _closing_replicas;
-    closed_replicas _closed_replicas;
+    replica_map_by_gpid _replicas;
+    opening_replica_map_by_gpid _opening_replicas;
+    closing_replica_map_by_gpid _closing_replicas;
+    closed_replica_map_by_gpid _closed_replicas;
 
     ::dsn::host_port _primary_host_port;
     // The stringify of '_primary_host_port', used by logging usually.
diff --git a/src/replica/test/load_replicas_test.cpp b/src/replica/test/load_replicas_test.cpp
index a6ca7aecc3..2e6c08808a 100644
--- a/src/replica/test/load_replicas_test.cpp
+++ b/src/replica/test/load_replicas_test.cpp
@@ -103,7 +103,7 @@ class mock_load_replica : public replica_stub
         PRESERVE_FLAG(max_replicas_on_load_for_each_disk);
         FLAGS_max_replicas_on_load_for_each_disk = max_replicas_on_load_for_each_disk;
 
-        replicas actual_loaded_replicas;
+        replica_stub::replica_map_by_gpid actual_loaded_replicas;
         load_replicas(actual_loaded_replicas);
         ASSERT_EQ(_expected_loaded_replicas, actual_loaded_replicas);
 
@@ -197,7 +197,7 @@ class mock_load_replica : public replica_stub
     std::vector<size_t> _disk_loaded_replicas_for_order;
 
     mutable std::mutex _mtx;
-    replicas _expected_loaded_replicas;
+    replica_stub::replica_map_by_gpid _expected_loaded_replicas;
 
     DISALLOW_COPY_AND_ASSIGN(mock_load_replica);
     DISALLOW_MOVE_AND_ASSIGN(mock_load_replica);