diff --git a/lua/apisix.lua b/lua/apisix.lua
index 9c899d64..6d191896 100644
--- a/lua/apisix.lua
+++ b/lua/apisix.lua
@@ -1,8 +1,7 @@
 -- Copyright (C) Yuansheng Wang
 
 local require = require
-local log = require("apisix.core.log")
-local resp = require("apisix.core.resp")
+local core = require("apisix.core")
 local route_handler = require("apisix.route.handler")
 local base_plugin = require("apisix.base_plugin")
 local new_tab = require("table.new")
@@ -11,8 +10,10 @@ local ngx = ngx
 local ngx_req = ngx.req
 local ngx_var = ngx.var
 
+
 local _M = {version = 0.1}
 
+
 function _M.init()
     require("resty.core")
     require("ngx.re").opt("jit_stack_size", 200 * 1024)
@@ -24,10 +25,13 @@ function _M.init()
     require("apisix.route.handler").init()
 end
 
+
 function _M.init_worker()
     require("apisix.route.load").init_worker()
+    require("apisix.balancer").init_worker()
 end
 
+
 function _M.rewrite_phase()
     local ngx_ctx = ngx.ctx
     local api_ctx = ngx_ctx.api_ctx
@@ -52,8 +56,8 @@ function _M.rewrite_phase()
     end
 
     if not ok then
-        log.info("not find any matched route")
-        return resp(404)
+        core.log.info("not find any matched route")
+        return core.resp(404)
     end
 
     -- todo: move those code to another single file
diff --git a/lua/apisix/balancer.lua b/lua/apisix/balancer.lua
index 8b7acdc9..de01b1ee 100644
--- a/lua/apisix/balancer.lua
+++ b/lua/apisix/balancer.lua
@@ -1,14 +1,17 @@
 local core = require("apisix.core")
-local resty_roundrobin = require("resty.roundrobin")
+local config_etcd = require("apisix.core.config_etcd")
+local roundrobin = require("resty.roundrobin")
 local balancer = require("ngx.balancer")
 local lrucache = require("resty.lrucache")
+local upstreams_etcd
 local ngx = ngx
 local ngx_exit = ngx.exit
 local ngx_ERROR = ngx.ERROR
+local error = error
 
 
 local module_name = "balancer"
-local cache, err = lrucache.new(500)    -- todo: config in yaml
+local cache = lrucache.new(500)    -- todo: config in yaml
 
 
 local _M = {
@@ -17,16 +20,16 @@ local _M = {
 }
 
 
-local function create_obj(typ, nodes)
+local function create_server_piker(typ, nodes)
     -- core.log.info("create create_obj, type: ", typ,
     --               " nodes: ", core.json.encode(nodes))
 
     if typ == "roundrobin" then
-        local obj = resty_roundrobin:new(nodes)
-        return obj
+        return roundrobin:new(nodes)
     end
 
     if typ == "chash" then
+        -- todo: support `chash`
         return nil, "not supported balancer type: " .. typ, 0
     end
 
@@ -37,30 +40,55 @@ end
 function _M.run(route, version)
     -- core.log.warn("conf: ", core.json.encode(conf), " version: ", version)
     local upstream = route.value.upstream
+    local up_id = upstream.id
 
-    local key = upstream.type .. "#" .. route.id .. "#" .. version
+    local key
+    if up_id then
+        if not upstreams_etcd then
+            core.log.warn("need to create a etcd instance for fetching ",
+                          "upstream information")
+            ngx_exit(ngx_ERROR)
+            return
+        end
+
+        local upstream_obj = upstreams_etcd:get(up_id)
+        if not upstream_obj then
+            core.log.warn("failed to find upstream by id: ", up_id)
+            ngx_exit(ngx_ERROR)
+            return
+        end
+        -- core.log.info("upstream: ", core.json.encode(upstream_obj))
+
+        upstream = upstream_obj.value
+        key = upstream.type .. "#upstream_" .. up_id .. "#"
+              .. upstream_obj.modifiedIndex
+
+    else
+        key = upstream.type .. "#route_" .. route.id .. "#" .. version
+    end
+
+    local server_piker, stale_server_piker = cache:get(key)
+    if not server_piker then
+        if stale_server_piker and stale_server_piker.conf_version == version then
+            server_piker = stale_server_piker
 
-    local obj, stale_obj = cache:get(key)
-    if not obj then
-        if stale_obj and stale_obj.conf_version == version then
-            obj = stale_obj
         else
-            obj, err = create_obj(upstream.type, upstream.nodes)
-            if not obj then
-                core.log.error("failed to get balancer object: ", err)
+            local err
+            server_piker, err = create_server_piker(upstream.type, upstream.nodes)
+            if not server_piker then
+                core.log.error("failed to get server piker: ", err)
                 ngx_exit(ngx_ERROR)
                 return
             end
-            obj.conf_version = version
+            server_piker.conf_version = version
         end
 
         -- todo: need a way to clean the old cache
         -- todo: config in yaml
-        cache:set(key, obj, 3600)
+        cache:set(key, server_piker, 3600)
     end
 
-    local server
-    server, err = obj:find()
+    local server, err = server_piker:find()
     if not server then
         core.log.error("failed to find valid upstream server", err)
         ngx_exit(ngx_ERROR)
@@ -77,4 +105,15 @@ function _M.run(route, version)
 end
 
 
+function _M.init_worker()
+    local err
+    upstreams_etcd, err = config_etcd.new("/user_upstreams",
+                                          {automatic = true})
+    if not upstreams_etcd then
+        error("failed to create etcd instance to fetch upstream: " .. err)
+        return
+    end
+end
+
+
 return _M
diff --git a/lua/apisix/core.lua b/lua/apisix/core.lua
index 70416923..a7d49ba3 100644
--- a/lua/apisix/core.lua
+++ b/lua/apisix/core.lua
@@ -2,10 +2,11 @@ return {
     version = 0.1,
     log = require("apisix.core.log"),
     config = require("apisix.core.config"),
-    config_etcd = require("apisix.core.config_etcd"),
     json = require("cjson.safe"),
     table = {
-        new = require("table.new"),
+        new   = require("table.new"),
         clear = require("table.clear"),
+        nkeys = require("table.nkeys"),
     },
+    resp = require("apisix.core.resp"),
 }
diff --git a/lua/apisix/core/config_etcd.lua b/lua/apisix/core/config_etcd.lua
index 7b866dfc..97afba68 100644
--- a/lua/apisix/core/config_etcd.lua
+++ b/lua/apisix/core/config_etcd.lua
@@ -3,7 +3,6 @@
 local core = require("apisix.core")
 local etcd = require("resty.etcd")
 local new_tab = require("table.new")
-local json_encode = require("cjson.safe").encode
 local exiting = ngx.worker.exiting
 local insert_tab = table.insert
 local type = type
@@ -11,6 +10,7 @@ local ipairs = ipairs
 local setmetatable = setmetatable
 local ngx_sleep = ngx.sleep
 local ngx_timer_at = ngx.timer.at
+local sub_str = string.sub
 
 
 local _M = {version = 0.1}
@@ -62,11 +62,12 @@ local function waitdir(etcd_cli, key, modified_index)
 end
 
 
-function _M.fetch(self)
-    if self.automatic then
-        return self.values
-    end
+local function short_key(self, str)
+    return sub_str(str, #self.key + 2)
+end
 
+
+function _M.fetch(self)
     if self.values == nil then
         local dir_res, err = readdir(self.etcd_cli, self.key)
         if not dir_res then
@@ -82,7 +83,8 @@ function _M.fetch(self)
 
         for _, item in ipairs(dir_res.nodes) do
             insert_tab(self.values, item)
-            self.values_hash[item.key] = #self.values
+            local key = short_key(self, item.key)
+            self.values_hash[key] = #self.values
 
             if not self.prev_index or item.modifiedIndex > self.prev_index then
                 self.prev_index = item.modifiedIndex
@@ -92,43 +94,71 @@ function _M.fetch(self)
         return self.values
     end
 
-    local dir_res, err = waitdir(self.etcd_cli, self.key, self.prev_index + 1)
-    if not dir_res then
+    local res, err = waitdir(self.etcd_cli, self.key, self.prev_index + 1)
+    if not res then
         return nil, err
     end
 
-    if dir_res.dir then
+    if res.dir then
         core.log.error("todo: support for parsing `dir` response structures. ",
-                       json_encode(dir_res))
+                       core.json.encode(res))
         return self.values
     end
-    -- log.warn("waitdir: ", require("cjson").encode(dir_res))
+    -- core.log.warn("waitdir: ", core.json.encode(res))
 
-    if not self.prev_index or dir_res.modifiedIndex > self.prev_index then
-        self.prev_index = dir_res.modifiedIndex
+    if not self.prev_index or res.modifiedIndex > self.prev_index then
+        self.prev_index = res.modifiedIndex
     end
 
-    local pre_index = self.values_hash[dir_res.key]
+    local key = short_key(self, res.key)
+    local pre_index = self.values_hash[key]
     if pre_index then
-        if dir_res.value then
-            self.values[pre_index] = dir_res.value
+        if res.value then
+            self.values[pre_index] = res
 
         else
+            self.sync_times = self.sync_times + 1
             self.values[pre_index] = false
         end
 
-        return self.values
+    elseif res.value then
+        insert_tab(self.values, res)
+        self.values_hash[key] = #self.values
     end
 
-    if dir_res.value then
-        insert_tab(self.values, dir_res)
-        self.values_hash[dir_res.key] = #self.values
+    -- avoid space waste
+    -- todo: need to cover this path, it is important.
+    if self.sync_times > 100 then
+        local count = 0
+        for i = 1, #self.values do
+            local val = self.values[i]
+            self.values[i] = nil
+            if val then
+                count = count + 1
+                self.values[count] = val
+            end
+        end
+
+        for i = 1, count do
+            key = short_key(self, self.values[i].key)
+            self.values_hash[key] = i
+        end
     end
 
     return self.values
 end
 
 
+function _M.get(self, key)
+    local arr_idx = self.values_hash[tostring(key)]
+    if not arr_idx then
+        return nil
+    end
+
+    return self.values[arr_idx]
+end
+
+
 local function _automatic_fetch(premature, self)
     if premature then
         return
@@ -169,6 +199,7 @@ function _M.new(key, opts)
         prev_index = nil,
         key = key,
         automatic = automatic,
+        sync_times = 0,
     }, mt)
 
     if automatic then
diff --git a/lua/apisix/route/handler.lua b/lua/apisix/route/handler.lua
index da0a47e8..28e09f21 100644
--- a/lua/apisix/route/handler.lua
+++ b/lua/apisix/route/handler.lua
@@ -3,7 +3,7 @@
 local r3router = require("resty.r3")
 local new_tab = require("table.new")
 local route_load = require("apisix.route.load")
-local log = require("apisix.core.log")
+local core = require("apisix.core")
 local ipairs = ipairs
 
 local router
@@ -15,7 +15,7 @@ local _M = {}
 local function run_route(matched_params, route, api_ctx)
     api_ctx.matched_params = matched_params
     api_ctx.matched_route = route
-    -- log.warn("run route id: ", route.id, " host: ", api_ctx.host)
+    -- core.log.warn("run route id: ", route.id, " host: ", api_ctx.host)
 end
 
 
@@ -48,12 +48,12 @@ do
     local routes = {}
 function _M.set_routes(new_routes)
     routes = new_routes
-    log.info("update new routes: ", require("cjson.safe").encode(routes))
+    core.log.info("update new routes: ", require("cjson.safe").encode(routes))
 end
 
 function _M.get_router()
     if router == nil then
-        log.info("generate a empty router instance")
+        core.log.info("generate a empty router instance")
         return _load_route(routes)
     end
 
diff --git a/lua/apisix/route/load.lua b/lua/apisix/route/load.lua
index 078d02c2..31dd15b5 100644
--- a/lua/apisix/route/load.lua
+++ b/lua/apisix/route/load.lua
@@ -1,9 +1,7 @@
 -- Copyright (C) Yuansheng Wang
 
-local log = require("apisix.core.log")
+local core = require("apisix.core")
 local etcd = require("apisix.core.config_etcd")
-local table_nkeys = require("table.nkeys")
-local new_tab = require("table.new")
 local insert_tab = table.insert
 local ngx = ngx
 local pcall = pcall
@@ -18,12 +16,12 @@ local function load(etcd_routes)
     local routes, err = etcd_routes:fetch()
     if not routes then
         if err ~= "timeout" then
-            log.error("failed to fetch routes: ", err)
+            core.log.error("failed to fetch routes: ", err)
         end
         return
     end
 
-    local arr_routes = new_tab(table_nkeys(routes), 0)
+    local arr_routes = core.table.new(core.table.nkeys(routes), 0)
     for route_id, route in pairs(routes) do
         if type(route) == "table" then
             route.id = route_id
@@ -31,7 +29,7 @@ local function load(etcd_routes)
         end
     end
 
-    -- log.warn(apisix.json.encode(arr_routes))
+    -- core.log.warn(apisix.json.encode(arr_routes))
     if callback then
         callback(arr_routes)
     end
@@ -56,7 +54,7 @@ function _M.load(premature)
     running = false
 
     if not ok then
-        log.error("failed to call `load` function: ", err)
+        core.log.error("failed to call `load` function: ", err)
     end
 end