diff --git a/src/memchunk.h b/src/memchunk.h
index c00c1e60..533832dc 100644
--- a/src/memchunk.h
+++ b/src/memchunk.h
@@ -229,9 +229,9 @@ template <typename Memchunk> struct Memchunks {
   size_t len;
 };
 
-using Memchunk4K = Memchunk<4096>;
-using MemchunkPool4K = Pool<Memchunk4K>;
-using Memchunks4K = Memchunks<Memchunk4K>;
+using Memchunk16K = Memchunk<16384>;
+using MemchunkPool = Pool<Memchunk16K>;
+using DefaultMemchunks = Memchunks<Memchunk16K>;
 
 } // namespace nghttp2
 
diff --git a/src/memchunk_test.cc b/src/memchunk_test.cc
index 7cba39ed..15317347 100644
--- a/src/memchunk_test.cc
+++ b/src/memchunk_test.cc
@@ -33,7 +33,7 @@
 namespace nghttp2 {
 
 void test_pool_recycle(void) {
-  MemchunkPool4K pool;
+  MemchunkPool pool;
 
   CU_ASSERT(!pool.pool);
   CU_ASSERT(0 == pool.poolsize);
@@ -42,13 +42,13 @@ void test_pool_recycle(void) {
   auto m1 = pool.get();
 
   CU_ASSERT(m1 == pool.pool.get());
-  CU_ASSERT(MemchunkPool4K::value_type::size == pool.poolsize);
+  CU_ASSERT(MemchunkPool::value_type::size == pool.poolsize);
   CU_ASSERT(nullptr == pool.freelist);
 
   auto m2 = pool.get();
 
   CU_ASSERT(m2 == pool.pool.get());
-  CU_ASSERT(2 * MemchunkPool4K::value_type::size == pool.poolsize);
+  CU_ASSERT(2 * MemchunkPool::value_type::size == pool.poolsize);
   CU_ASSERT(nullptr == pool.freelist);
   CU_ASSERT(m1 == m2->knext.get());
   CU_ASSERT(nullptr == m1->knext.get());
@@ -56,20 +56,20 @@ void test_pool_recycle(void) {
   auto m3 = pool.get();
 
   CU_ASSERT(m3 == pool.pool.get());
-  CU_ASSERT(3 * MemchunkPool4K::value_type::size == pool.poolsize);
+  CU_ASSERT(3 * MemchunkPool::value_type::size == pool.poolsize);
   CU_ASSERT(nullptr == pool.freelist);
 
   pool.recycle(m3);
 
   CU_ASSERT(m3 == pool.pool.get());
-  CU_ASSERT(3 * MemchunkPool4K::value_type::size == pool.poolsize);
+  CU_ASSERT(3 * MemchunkPool::value_type::size == pool.poolsize);
   CU_ASSERT(m3 == pool.freelist);
 
   auto m4 = pool.get();
 
   CU_ASSERT(m3 == m4);
   CU_ASSERT(m4 == pool.pool.get());
-  CU_ASSERT(3 * MemchunkPool4K::value_type::size == pool.poolsize);
+  CU_ASSERT(3 * MemchunkPool::value_type::size == pool.poolsize);
   CU_ASSERT(nullptr == pool.freelist);
 
   pool.recycle(m2);
diff --git a/src/shrpx.cc b/src/shrpx.cc
index 6eb08f68..986ff666 100644
--- a/src/shrpx.cc
+++ b/src/shrpx.cc
@@ -748,7 +748,7 @@ void fill_default_config() {
   mod_config()->auto_tls_ticket_key = true;
   mod_config()->tls_ctx_per_worker = false;
   mod_config()->downstream_request_buffer_size = 16 * 1024;
-  mod_config()->downstream_response_buffer_size = 64 * 1024;
+  mod_config()->downstream_response_buffer_size = 16 * 1024;
 }
 } // namespace
 
diff --git a/src/shrpx_downstream.cc b/src/shrpx_downstream.cc
index eb065406..d844b6e2 100644
--- a/src/shrpx_downstream.cc
+++ b/src/shrpx_downstream.cc
@@ -477,7 +477,7 @@ bool Downstream::request_buf_full() {
   }
 }
 
-Memchunks4K *Downstream::get_request_buf() { return &request_buf_; }
+DefaultMemchunks *Downstream::get_request_buf() { return &request_buf_; }
 
 // Call this function after this object is attached to
 // Downstream. Otherwise, the program will crash.
@@ -664,7 +664,7 @@ void Downstream::set_response_state(int state) { response_state_ = state; }
 
 int Downstream::get_response_state() const { return response_state_; }
 
-Memchunks4K *Downstream::get_response_buf() { return &response_buf_; }
+DefaultMemchunks *Downstream::get_response_buf() { return &response_buf_; }
 
 bool Downstream::response_buf_full() {
   if (dconn_) {
diff --git a/src/shrpx_downstream.h b/src/shrpx_downstream.h
index 746597db..76a0065e 100644
--- a/src/shrpx_downstream.h
+++ b/src/shrpx_downstream.h
@@ -181,7 +181,7 @@ public:
   };
   void set_request_state(int state);
   int get_request_state() const;
-  Memchunks4K *get_request_buf();
+  DefaultMemchunks *get_request_buf();
   // downstream response API
   const Headers &get_response_headers() const;
   // Lower the response header field names and indexes response
@@ -224,7 +224,7 @@ public:
   void set_response_connection_close(bool f);
   void set_response_state(int state);
   int get_response_state() const;
-  Memchunks4K *get_response_buf();
+  DefaultMemchunks *get_response_buf();
   bool response_buf_full();
   void add_response_bodylen(size_t amount);
   int64_t get_response_bodylen() const;
@@ -305,8 +305,8 @@ private:
   std::chrono::high_resolution_clock::time_point request_start_time_;
   std::string assembled_request_cookie_;
 
-  Memchunks4K request_buf_;
-  Memchunks4K response_buf_;
+  DefaultMemchunks request_buf_;
+  DefaultMemchunks response_buf_;
 
   ev_timer upstream_rtimer_;
   ev_timer upstream_wtimer_;
diff --git a/src/shrpx_http2_upstream.cc b/src/shrpx_http2_upstream.cc
index 9c30535f..b6f7e731 100644
--- a/src/shrpx_http2_upstream.cc
+++ b/src/shrpx_http2_upstream.cc
@@ -1375,6 +1375,6 @@ int Http2Upstream::on_downstream_reset() {
   return 0;
 }
 
-MemchunkPool4K *Http2Upstream::get_mcpool() { return &mcpool_; }
+MemchunkPool *Http2Upstream::get_mcpool() { return &mcpool_; }
 
 } // namespace shrpx
diff --git a/src/shrpx_http2_upstream.h b/src/shrpx_http2_upstream.h
index adaf19a3..c0d21f46 100644
--- a/src/shrpx_http2_upstream.h
+++ b/src/shrpx_http2_upstream.h
@@ -82,7 +82,7 @@ public:
   virtual void on_handler_delete();
   virtual int on_downstream_reset();
 
-  virtual MemchunkPool4K *get_mcpool();
+  virtual MemchunkPool *get_mcpool();
 
   bool get_flow_control() const;
   // Perform HTTP/2 upgrade from |upstream|. On success, this object
@@ -100,7 +100,7 @@ public:
 private:
   // must be put before downstream_queue_
   std::unique_ptr<HttpsUpstream> pre_upstream_;
-  MemchunkPool4K mcpool_;
+  MemchunkPool mcpool_;
   DownstreamQueue downstream_queue_;
   ev_timer settings_timer_;
   ClientHandler *handler_;
diff --git a/src/shrpx_https_upstream.cc b/src/shrpx_https_upstream.cc
index adae37f1..18c4640a 100644
--- a/src/shrpx_https_upstream.cc
+++ b/src/shrpx_https_upstream.cc
@@ -852,6 +852,6 @@ int HttpsUpstream::on_downstream_reset() {
   return 0;
 }
 
-MemchunkPool4K *HttpsUpstream::get_mcpool() { return &mcpool_; }
+MemchunkPool *HttpsUpstream::get_mcpool() { return &mcpool_; }
 
 } // namespace shrpx
diff --git a/src/shrpx_https_upstream.h b/src/shrpx_https_upstream.h
index 694d056b..895f91ef 100644
--- a/src/shrpx_https_upstream.h
+++ b/src/shrpx_https_upstream.h
@@ -76,7 +76,7 @@ public:
   virtual void on_handler_delete();
   virtual int on_downstream_reset();
 
-  virtual MemchunkPool4K *get_mcpool();
+  virtual MemchunkPool *get_mcpool();
 
   void reset_current_header_length();
   void log_response_headers(const std::string &hdrs) const;
@@ -86,7 +86,7 @@ private:
   http_parser htp_;
   size_t current_header_length_;
   // must be put before downstream_
-  MemchunkPool4K mcpool_;
+  MemchunkPool mcpool_;
   std::unique_ptr<Downstream> downstream_;
   IOControl ioctrl_;
 };
diff --git a/src/shrpx_spdy_upstream.cc b/src/shrpx_spdy_upstream.cc
index 9b9629be..28bb4eb4 100644
--- a/src/shrpx_spdy_upstream.cc
+++ b/src/shrpx_spdy_upstream.cc
@@ -1060,6 +1060,6 @@ int SpdyUpstream::on_downstream_reset() {
   return 0;
 }
 
-MemchunkPool4K *SpdyUpstream::get_mcpool() { return &mcpool_; }
+MemchunkPool *SpdyUpstream::get_mcpool() { return &mcpool_; }
 
 } // namespace shrpx
diff --git a/src/shrpx_spdy_upstream.h b/src/shrpx_spdy_upstream.h
index b2753c3f..639af319 100644
--- a/src/shrpx_spdy_upstream.h
+++ b/src/shrpx_spdy_upstream.h
@@ -77,7 +77,7 @@ public:
   virtual void on_handler_delete();
   virtual int on_downstream_reset();
 
-  virtual MemchunkPool4K *get_mcpool();
+  virtual MemchunkPool *get_mcpool();
 
   bool get_flow_control() const;
 
@@ -88,7 +88,7 @@ public:
 
 private:
   // must be put before downstream_queue_
-  MemchunkPool4K mcpool_;
+  MemchunkPool mcpool_;
   DownstreamQueue downstream_queue_;
   ClientHandler *handler_;
   spdylay_session *session_;
diff --git a/src/shrpx_upstream.h b/src/shrpx_upstream.h
index 9f2792db..3358510e 100644
--- a/src/shrpx_upstream.h
+++ b/src/shrpx_upstream.h
@@ -65,7 +65,7 @@ public:
   virtual int resume_read(IOCtrlReason reason, Downstream *downstream,
                           size_t consumed) = 0;
 
-  virtual MemchunkPool4K *get_mcpool() = 0;
+  virtual MemchunkPool *get_mcpool() = 0;
 };
 
 } // namespace shrpx