diff --git a/include/dsn/cpp/json_helper.h b/include/dsn/cpp/json_helper.h
index 3062df9687..feeaf712f9 100644
--- a/include/dsn/cpp/json_helper.h
+++ b/include/dsn/cpp/json_helper.h
@@ -550,10 +550,7 @@ class json_forwarder
     {
         std::ostringstream os;
         encode(os, t);
-        std::string *result = new std::string(os.str());
-        return dsn::blob(std::shared_ptr<char>(const_cast<char *>(result->c_str()),
-                                               [result](char *) { delete result; }),
-                         result->length());
+        return blob::create_from_bytes(os.str());
     }
 
     static bool decode(const JsonObject &in, T &t)
diff --git a/include/dsn/tool-api/task_spec.h b/include/dsn/tool-api/task_spec.h
index 42649daa11..2aa78b1e42 100644
--- a/include/dsn/tool-api/task_spec.h
+++ b/include/dsn/tool-api/task_spec.h
@@ -39,7 +39,6 @@
 #include <dsn/utility/config_helper.h>
 #include <dsn/utility/enum_helper.h>
 #include <dsn/utility/customizable_id.h>
-#include <dsn/utility/singleton_vector_store.h>
 #include <dsn/utility/join_point.h>
 #include <dsn/utility/extensible_object.h>
 #include <dsn/utility/exp_delay.h>
diff --git a/include/dsn/utility/singleton_vector_store.h b/include/dsn/utility/singleton_vector_store.h
deleted file mode 100644
index 49c9f72866..0000000000
--- a/include/dsn/utility/singleton_vector_store.h
+++ /dev/null
@@ -1,93 +0,0 @@
-/*
- * The MIT License (MIT)
- *
- * Copyright (c) 2015 Microsoft Corporation
- *
- * -=- Robust Distributed System Nucleus (rDSN) -=-
- *
- * Permission is hereby granted, free of charge, to any person obtaining a copy
- * of this software and associated documentation files (the "Software"), to deal
- * in the Software without restriction, including without limitation the rights
- * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
- * copies of the Software, and to permit persons to whom the Software is
- * furnished to do so, subject to the following conditions:
- *
- * The above copyright notice and this permission notice shall be included in
- * all copies or substantial portions of the Software.
- *
- * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
- * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
- * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
- * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
- * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
- * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
- * THE SOFTWARE.
- */
-
-/*
- * Description:
- *     What is this file about?
- *
- * Revision history:
- *     xxxx-xx-xx, author, first version
- *     xxxx-xx-xx, author, fix bug about xxx
- */
-
-#pragma once
-
-#include <dsn/utility/singleton.h>
-#include <vector>
-
-namespace dsn {
-namespace utils {
-
-template <typename T, T default_value>
-class singleton_vector_store
-    : public dsn::utils::singleton<singleton_vector_store<T, default_value>>
-{
-public:
-    singleton_vector_store(void) {}
-    ~singleton_vector_store(void) {}
-
-    bool contains(int index) const
-    {
-        if (index >= static_cast<int>(_contains.size()))
-            return false;
-        else
-            return _contains[index];
-    }
-
-    T get(int index) const
-    {
-        if (index >= static_cast<int>(_contains.size()))
-            return default_value;
-        else
-            return _values[index];
-    }
-
-    bool put(int index, T value)
-    {
-        if (index >= static_cast<int>(_contains.size())) {
-            for (int i = static_cast<int>(_contains.size()); i < index; i++) {
-                _contains.push_back(false);
-                _values.push_back(default_value);
-            }
-
-            _contains.push_back(true);
-            _values.push_back(value);
-            return true;
-        } else if (_contains[index])
-            return false;
-        else {
-            _contains[index] = true;
-            _values[index] = value;
-            return true;
-        }
-    }
-
-private:
-    std::vector<bool> _contains;
-    std::vector<T> _values;
-};
-}
-} // end namespace dsn::utils
diff --git a/src/core/core/task_spec.cpp b/src/core/core/task_spec.cpp
index 4de6979a43..d484eeb6cb 100644
--- a/src/core/core/task_spec.cpp
+++ b/src/core/core/task_spec.cpp
@@ -34,24 +34,26 @@
  */
 
 #include <dsn/tool-api/task_spec.h>
-#include <dsn/utility/singleton.h>
-#include <dsn/perf_counter/perf_counter.h>
 #include <dsn/tool-api/command_manager.h>
 #include <dsn/tool-api/threadpool_spec.h>
-#include <sstream>
-#include <vector>
-#include <thread>
+#include <dsn/utility/smart_pointers.h>
 
 namespace dsn {
 
+constexpr int TASK_SPEC_STORE_CAPACITY = 512;
+
+// A sequential storage maps task_code to task_spec.
+static std::array<std::unique_ptr<task_spec>, TASK_SPEC_STORE_CAPACITY> s_task_spec_store;
+
 void task_spec::register_task_code(task_code code,
                                    dsn_task_type_t type,
                                    dsn_task_priority_t pri,
                                    dsn::threadpool_code pool)
 {
-    if (!dsn::utils::singleton_vector_store<task_spec *, nullptr>::instance().contains(code)) {
-        task_spec *spec = new task_spec(code, code.to_string(), type, pri, pool);
-        dsn::utils::singleton_vector_store<task_spec *, nullptr>::instance().put(code, spec);
+    dassert(code < TASK_SPEC_STORE_CAPACITY, "code = %d", code);
+    if (!s_task_spec_store[code]) {
+        s_task_spec_store[code] = make_unique<task_spec>(code, code.to_string(), type, pri, pool);
+        auto &spec = s_task_spec_store[code];
 
         if (type == TASK_TYPE_RPC_REQUEST) {
             std::string ack_name = std::string(code.to_string()) + std::string("_ACK");
@@ -114,7 +116,7 @@ void task_spec::register_storage_task_code(task_code code,
 
 task_spec *task_spec::get(int code)
 {
-    return dsn::utils::singleton_vector_store<task_spec *, nullptr>::instance().get(code);
+    return code < TASK_SPEC_STORE_CAPACITY ? s_task_spec_store[code].get() : nullptr;
 }
 
 task_spec::task_spec(int code,