diff --git a/apisix/consumer.lua b/apisix/consumer.lua
index 31dfa05c80f3..35f01329d82b 100644
--- a/apisix/consumer.lua
+++ b/apisix/consumer.lua
@@ -74,6 +74,15 @@ function _M.plugin(plugin_name)
 end
 
 
+function _M.consumers()
+    if not consumers then
+        return nil, nil
+    end
+
+    return consumers.values, consumers.conf_version
+end
+
+
 function _M.init_worker()
     local err
     consumers, err = core.config.new("/consumers", {
diff --git a/apisix/core/config_etcd.lua b/apisix/core/config_etcd.lua
index fbb6df8dbf5d..6e616b08f906 100644
--- a/apisix/core/config_etcd.lua
+++ b/apisix/core/config_etcd.lua
@@ -49,6 +49,26 @@ local mt = {
     end
 }
 
+
+local function getkey(etcd_cli, key)
+    if not etcd_cli then
+        return nil, "not inited"
+    end
+
+    local res, err = etcd_cli:get(key)
+    if not res then
+        -- log.error("failed to get key from etcd: ", err)
+        return nil, err
+    end
+
+    if type(res.body) ~= "table" then
+        return nil, "failed to get key from etcd"
+    end
+
+    return res
+end
+
+
 local function readdir(etcd_cli, key)
     if not etcd_cli then
         return nil, nil, "not inited"
@@ -67,12 +87,12 @@ local function readdir(etcd_cli, key)
     return res
 end
 
-local function waitdir(etcd_cli, key, modified_index)
+local function waitdir(etcd_cli, key, modified_index, timeout)
     if not etcd_cli then
         return nil, nil, "not inited"
     end
 
-    local res, err = etcd_cli:waitdir(key, modified_index)
+    local res, err = etcd_cli:waitdir(key, modified_index, timeout)
     if not res then
         -- log.error("failed to get key from etcd: ", err)
         return nil, err
@@ -201,9 +221,25 @@ local function sync_data(self)
         return true
     end
 
-    local dir_res, err = waitdir(self.etcd_cli, self.key, self.prev_index + 1)
+    -- for fetch the etcd index
+    local key_res, _ = getkey(self.etcd_cli, self.key)
+
+    local dir_res, err = waitdir(self.etcd_cli, self.key, self.prev_index + 1, self.timeout)
+
     log.info("waitdir key: ", self.key, " prev_index: ", self.prev_index + 1)
     log.info("res: ", json.delay_encode(dir_res, true))
+    if err == "timeout" then
+        if key_res and key_res.headers then
+            local key_index = key_res.headers["X-Etcd-Index"]
+            local key_idx = key_index and tonumber(key_index) or 0
+            if key_idx and key_idx > self.prev_index then
+                -- Avoid the index to exceed 1000 by updating other keys
+                -- that will causing a full reload
+                self:upgrade_version(key_index)
+            end
+        end
+    end
+
     if not dir_res then
         return false, err
     end
@@ -330,6 +366,15 @@ function _M.get(self, key)
 end
 
 
+function _M.getkey(self, key)
+    if not self.running then
+        return nil, "stoped"
+    end
+
+    return getkey(self.etcd_cli, key)
+end
+
+
 local function _automatic_fetch(premature, self)
     if premature then
         return
@@ -395,6 +440,7 @@ function _M.new(key, opts)
     local automatic = opts and opts.automatic
     local item_schema = opts and opts.item_schema
     local filter_fun = opts and opts.filter
+    local timeout = opts and opts.timeout
 
     local obj = setmetatable({
         etcd_cli = etcd_cli,
@@ -410,6 +456,7 @@ function _M.new(key, opts)
         prev_index = nil,
         last_err = nil,
         last_err_time = nil,
+        timeout = timeout,
         filter = filter_fun,
     }, mt)
 
diff --git a/apisix/http/router/radixtree_sni.lua b/apisix/http/router/radixtree_sni.lua
index d042aeedc957..07c689fa8033 100644
--- a/apisix/http/router/radixtree_sni.lua
+++ b/apisix/http/router/radixtree_sni.lua
@@ -204,6 +204,15 @@ function _M.match_and_set(api_ctx)
 end
 
 
+function _M.ssls()
+    if not ssl_certificates then
+        return nil, nil
+    end
+
+    return ssl_certificates.values, ssl_certificates.conf_version
+end
+
+
 function _M.init_worker()
     local err
     ssl_certificates, err = core.config.new("/ssl", {
diff --git a/apisix/plugins/grpc-transcode/proto.lua b/apisix/plugins/grpc-transcode/proto.lua
index 13f3060b1cd8..09240fa5a5b3 100644
--- a/apisix/plugins/grpc-transcode/proto.lua
+++ b/apisix/plugins/grpc-transcode/proto.lua
@@ -63,6 +63,15 @@ function _M.fetch(proto_id)
 end
 
 
+function _M.protos()
+    if not protos then
+        return nil, nil
+    end
+
+    return protos.values, protos.conf_version
+end
+
+
 function _M.init()
     local err
     protos, err = core.config.new("/proto", {
diff --git a/apisix/plugins/prometheus/exporter.lua b/apisix/plugins/prometheus/exporter.lua
index 2c0b6fc618ab..7e3d63eae7da 100644
--- a/apisix/plugins/prometheus/exporter.lua
+++ b/apisix/plugins/prometheus/exporter.lua
@@ -22,7 +22,19 @@ local ngx_capture = ngx.location.capture
 local re_gmatch = ngx.re.gmatch
 local tonumber = tonumber
 local select = select
+local type = type
 local prometheus
+local router = require("apisix.router")
+local get_routes = router.http_routes
+local get_ssls   = router.ssls
+local get_services = require("apisix.http.service").services
+local get_consumers = require("apisix.consumer").consumers
+local get_upstreams = require("apisix.upstream").upstreams
+local clear_tab = core.table.clear
+local get_stream_routes = router.stream_routes
+local get_protos = require("apisix.plugins.grpc-transcode.proto").protos
+
+
 
 -- Default set of latency buckets, 1ms to 60s:
 local DEFAULT_BUCKETS = { 1, 2, 5, 7, 10, 15, 20, 25, 30, 40, 50, 60, 70,
@@ -34,7 +46,6 @@ local metrics = {}
 
 
     local inner_tab_arr = {}
-    local clear_tab = core.table.clear
 local function gen_arr(...)
     clear_tab(inner_tab_arr)
 
@@ -56,7 +67,7 @@ function _M.init()
         return
     end
 
-    core.table.clear(metrics)
+    clear_tab(metrics)
 
     -- across all services
     prometheus = base_prometheus.init("prometheus-metrics", "apisix_")
@@ -67,6 +78,10 @@ function _M.init()
     metrics.etcd_reachable = prometheus:gauge("etcd_reachable",
             "Config server etcd reachable from APISIX, 0 is unreachable")
 
+    metrics.etcd_modify_indexes = prometheus:gauge("etcd_modify_indexes",
+            "Etcd modify index for APISIX keys",
+            {"key"})
+
     -- per service
     metrics.status = prometheus:counter("http_status",
             "HTTP status codes per service in APISIX",
@@ -152,13 +167,90 @@ local function nginx_status()
 
         label_values[1] = name
         metrics.connections:set(val[0], label_values)
+
     end
 end
 
 
+local key_values = {}
+local function set_modify_index(key, items, items_ver, global_max_index)
+    clear_tab(key_values)
+    local max_idx = 0
+    if items_ver and items then
+        for _, item in ipairs(items) do
+            if type(item) == "table" and item.modifiedIndex > max_idx then
+                max_idx = item.modifiedIndex
+            end
+        end
+    end
+
+    key_values[1] = key
+    metrics.etcd_modify_indexes:set(max_idx, key_values)
+
+
+    global_max_index = max_idx > global_max_index and max_idx or global_max_index
+
+    return global_max_index
+end
+
+
+local function etcd_modify_index()
+    clear_tab(key_values)
+    local global_max_idx = 0
+
+    -- routes
+    local routes, routes_ver = get_routes()
+    global_max_idx = set_modify_index("routes", routes, routes_ver, global_max_idx)
+
+    -- services
+    local services, services_ver = get_services()
+    global_max_idx = set_modify_index("services", services, services_ver, global_max_idx)
+
+    -- ssls
+    local ssls, ssls_ver = get_ssls()
+    global_max_idx = set_modify_index("ssls", ssls, ssls_ver, global_max_idx)
+
+    -- consumers
+    local consumers, consumers_ver = get_consumers()
+    global_max_idx = set_modify_index("consumers", consumers, consumers_ver, global_max_idx)
+
+    -- global_rules
+    local global_rules = router.global_rules
+    if global_rules then
+        global_max_idx = set_modify_index("global_rules", global_rules.values,
+            global_rules.conf_version, global_max_idx)
+
+        -- prev_index
+        key_values[1] = "prev_index"
+        metrics.etcd_modify_indexes:set(global_rules.prev_index, key_values)
+
+    else
+        global_max_idx = set_modify_index("global_rules", nil, nil, global_max_idx)
+    end
+
+    -- upstreams
+    local upstreams, upstreams_ver = get_upstreams()
+    global_max_idx = set_modify_index("upstreams", upstreams, upstreams_ver, global_max_idx)
+
+    -- stream_routes
+    local stream_routes, stream_routes_ver = get_stream_routes()
+    global_max_idx = set_modify_index("stream_routes", stream_routes,
+        stream_routes_ver, global_max_idx)
+
+    -- proto
+    local protos, protos_ver = get_protos()
+    global_max_idx = set_modify_index("protos", protos, protos_ver, global_max_idx)
+
+    -- global max
+    key_values[1] = "max_modify_index"
+    metrics.etcd_modify_indexes:set(global_max_idx, key_values)
+
+end
+
+
 function _M.collect()
     if not prometheus or not metrics then
-        core.log.err("prometheus: plugin is not initialized, please make sure ",
+        core.log.error("prometheus: plugin is not initialized, please make sure ",
                      " 'prometheus_metrics' shared dict is present in nginx template")
         return 500, {message = "An unexpected error occurred"}
     end
@@ -166,6 +258,9 @@ function _M.collect()
     -- across all services
     nginx_status()
 
+    -- etcd modify index
+    etcd_modify_index()
+
     -- config server status
     local config = core.config.new()
     local version, err = config:server_version()
@@ -178,6 +273,14 @@ function _M.collect()
                        "processing metrics endpoint: ", err)
     end
 
+    local res, _ = config:getkey("/routes")
+    if res and res.headers then
+        clear_tab(key_values)
+        -- global max
+        key_values[1] = "x_etcd_index"
+        metrics.etcd_modify_indexes:set(res.headers["X-Etcd-Index"], key_values)
+    end
+
     core.response.set_header("content_type", "text/plain")
     return 200, core.table.concat(prometheus:metric_data())
 end
diff --git a/apisix/router.lua b/apisix/router.lua
index 4ba870993717..b94be0c42f42 100644
--- a/apisix/router.lua
+++ b/apisix/router.lua
@@ -103,10 +103,22 @@ function _M.stream_init_worker()
 end
 
 
+function _M.ssls()
+    return _M.router_ssl.ssls()
+end
+
 function _M.http_routes()
     return _M.router_http.routes()
 end
 
+function _M.stream_routes()
+    -- maybe it's not inited.
+    if not _M.router_stream then
+        return nil, nil
+    end
+    return _M.router_stream.routes()
+end
+
 
 -- for test
 _M.filter_test = filter
diff --git a/apisix/schema_def.lua b/apisix/schema_def.lua
index d580be6982ed..34957ad8ae39 100644
--- a/apisix/schema_def.lua
+++ b/apisix/schema_def.lua
@@ -463,6 +463,7 @@ _M.service = {
 _M.consumer = {
     type = "object",
     properties = {
+        id = id_schema,
         username = {
             type = "string", minLength = 1, maxLength = 32,
             pattern = [[^[a-zA-Z0-9_]+$]]
diff --git a/t/core/etcd-sync.t b/t/core/etcd-sync.t
new file mode 100644
index 000000000000..ef0ea57cdf5b
--- /dev/null
+++ b/t/core/etcd-sync.t
@@ -0,0 +1,96 @@
+#
+# Licensed to the Apache Software Foundation (ASF) under one or more
+# contributor license agreements.  See the NOTICE file distributed with
+# this work for additional information regarding copyright ownership.
+# The ASF licenses this file to You under the Apache License, Version 2.0
+# (the "License"); you may not use this file except in compliance with
+# the License.  You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+use t::APISIX 'no_plan';
+
+no_root_location();
+
+run_tests;
+
+__DATA__
+
+=== TEST 1: auto update prev_index when other keys update
+--- config
+    location /t {
+        content_by_lua_block {
+            local core = require("apisix.core")
+
+            local consumers, _ = core.config.new("/consumers", {
+                automatic = true,
+                item_schema = core.schema.consumer,
+                timeout = 0.2
+            })
+
+            ngx.sleep(0.6)
+
+            local idx = consumers.prev_index
+            local key = "/test_key"
+            local val = "test_value"
+            core.etcd.set(key, val)
+
+            ngx.sleep(2)
+
+            local new_idx = consumers.prev_index
+
+            if new_idx > idx then
+                ngx.say("prev_index updated")
+            end
+        }
+    }
+--- request
+GET /t
+--- response_body
+prev_index updated
+--- no_error_log
+[error]
+
+
+
+=== TEST 2: using default timeout
+--- config
+    location /t {
+        content_by_lua_block {
+            local core = require("apisix.core")
+
+            local consumers, _ = core.config.new("/consumers", {
+                automatic = true,
+                item_schema = core.schema.consumer
+            })
+
+            ngx.sleep(0.6)
+            local idx = consumers.prev_index
+
+            local key = "/test_key"
+            local val = "test_value"
+            core.etcd.set(key, val)
+
+            ngx.sleep(2)
+
+            local new_idx = consumers.prev_index
+
+            if new_idx > idx then
+                ngx.say("prev_index updated")
+            else
+                ngx.say("prev_index not update")
+            end
+        }
+    }
+--- request
+GET /t
+--- response_body
+prev_index not update
+--- no_error_log
+[error]
diff --git a/t/plugin/prometheus.t b/t/plugin/prometheus.t
index 4e99b84d4a95..3a7d5c7584e1 100644
--- a/t/plugin/prometheus.t
+++ b/t/plugin/prometheus.t
@@ -663,3 +663,113 @@ GET /t
 passed
 --- no_error_log
 [error]
+
+
+
+=== TEST 32: fetch the prometheus metric data with `modify_indexes consumers`
+--- request
+GET /apisix/prometheus/metrics
+--- response_body_like eval
+qr/apisix_etcd_modify_indexes\{key="consumers"\} \d+/
+--- no_error_log
+[error]
+
+
+
+=== TEST 33: fetch the prometheus metric data with `modify_indexes global_rules`
+--- request
+GET /apisix/prometheus/metrics
+--- response_body_like eval
+qr/apisix_etcd_modify_indexes\{key="global_rules"\} \d+/
+--- no_error_log
+[error]
+
+
+
+=== TEST 34: fetch the prometheus metric data with `modify_indexes max_modify_index`
+--- request
+GET /apisix/prometheus/metrics
+--- response_body_like eval
+qr/apisix_etcd_modify_indexes\{key="max_modify_index"\} \d+/
+--- no_error_log
+[error]
+
+
+
+=== TEST 35: fetch the prometheus metric data with `modify_indexes protos`
+--- request
+GET /apisix/prometheus/metrics
+--- response_body_like eval
+qr/apisix_etcd_modify_indexes\{key="protos"\} \d+/
+--- no_error_log
+[error]
+
+
+
+=== TEST 36: fetch the prometheus metric data with `modify_indexes routes`
+--- request
+GET /apisix/prometheus/metrics
+--- response_body_like eval
+qr/apisix_etcd_modify_indexes\{key="routes"\} \d+/
+--- no_error_log
+[error]
+
+
+
+=== TEST 37: fetch the prometheus metric data with `modify_indexes services`
+--- request
+GET /apisix/prometheus/metrics
+--- response_body_like eval
+qr/apisix_etcd_modify_indexes\{key="services"\} \d+/
+--- no_error_log
+[error]
+
+
+
+=== TEST 38: fetch the prometheus metric data with `modify_indexes ssls`
+--- request
+GET /apisix/prometheus/metrics
+--- response_body_like eval
+qr/apisix_etcd_modify_indexes\{key="ssls"\} \d+/
+--- no_error_log
+[error]
+
+
+
+=== TEST 39: fetch the prometheus metric data with `modify_indexes stream_routes`
+--- request
+GET /apisix/prometheus/metrics
+--- response_body_like eval
+qr/apisix_etcd_modify_indexes\{key="stream_routes"\} \d+/
+--- no_error_log
+[error]
+
+
+
+=== TEST 40: fetch the prometheus metric data with `modify_indexes upstreams`
+--- request
+GET /apisix/prometheus/metrics
+--- response_body_like eval
+qr/apisix_etcd_modify_indexes\{key="upstreams"\} \d+/
+--- no_error_log
+[error]
+
+
+
+=== TEST 41: fetch the prometheus metric data with `modify_indexes prev_index`
+--- request
+GET /apisix/prometheus/metrics
+--- response_body_like eval
+qr/apisix_etcd_modify_indexes\{key="prev_index"\} \d+/
+--- no_error_log
+[error]
+
+
+
+=== TEST 42: fetch the prometheus metric data with `modify_indexes x_etcd_index`
+--- request
+GET /apisix/prometheus/metrics
+--- response_body_like eval
+qr/apisix_etcd_modify_indexes\{key="x_etcd_index"\} \d+/
+--- no_error_log
+[error]