diff --git a/src/dns_cache.c b/src/dns_cache.c
index 06a8d66..5b54996 100644
--- a/src/dns_cache.c
+++ b/src/dns_cache.c
@@ -329,7 +329,7 @@ static void _dns_cache_remove_by_domain(struct dns_cache_key *cache_key)
 			continue;
 		}
 
-		if (strncmp(dns_cache->info.dns_group_name, cache_key->dns_group_name, DNS_MAX_CNAME_LEN) != 0) {
+		if (strncmp(dns_cache->info.dns_group_name, cache_key->dns_group_name, DNS_GROUP_NAME_LEN) != 0) {
 			continue;
 		}
 
diff --git a/src/dns_client.c b/src/dns_client.c
index a441316..83812af 100644
--- a/src/dns_client.c
+++ b/src/dns_client.c
@@ -97,6 +97,7 @@ struct dns_server_info {
 	/* server type */
 	dns_server_type_t type;
 	long long so_mark;
+	int drop_packet_latency_ms;
 
 	/* client socket */
 	int fd;
@@ -118,6 +119,7 @@ struct dns_server_info {
 
 	time_t last_send;
 	time_t last_recv;
+	unsigned long send_tick;
 	int prohibit;
 
 	/* server addr info */
@@ -1056,6 +1058,7 @@ static int _dns_client_server_add(char *server_ip, char *server_host, int port,
 	server_info->skip_check_cert = skip_check_cert;
 	server_info->prohibit = 0;
 	server_info->so_mark = flags->set_mark;
+	server_info->drop_packet_latency_ms = flags->drop_packet_latency_ms;
 	safe_strncpy(server_info->proxy_name, flags->proxyname, sizeof(server_info->proxy_name));
 	pthread_mutex_init(&server_info->lock, NULL);
 	memcpy(&server_info->flags, flags, sizeof(server_info->flags));
@@ -2261,6 +2264,11 @@ static int _dns_client_process_udp(struct dns_server_info *server_info, struct e
 	/* update recv time */
 	time(&server_info->last_recv);
 
+	int latency = get_tick_count() - server_info->send_tick;
+	if (latency < server_info->drop_packet_latency_ms) {
+		return 0;
+	}
+
 	/* processing dns packet */
 	if (_dns_client_recv(server_info, inpacket, len, (struct sockaddr *)&from, from_len) != 0) {
 		return -1;
@@ -3326,6 +3334,7 @@ static int _dns_client_send_packet(struct dns_query_struct *query, void *packet,
 				continue;
 			}
 			time(&server_info->last_send);
+			server_info->send_tick = get_tick_count();
 		}
 		pthread_mutex_unlock(&client.server_list_lock);
 
diff --git a/src/dns_client.h b/src/dns_client.h
index 2b6adf1..cbdad7c 100644
--- a/src/dns_client.h
+++ b/src/dns_client.h
@@ -113,6 +113,7 @@ struct client_dns_server_flags {
 	unsigned int server_flag;
 	unsigned int result_flag;
 	long long set_mark;
+	int drop_packet_latency_ms;
 	char proxyname[DNS_MAX_CNAME_LEN];
 	union {
 		struct client_dns_server_flag_udp udp;
diff --git a/src/dns_conf.c b/src/dns_conf.c
index 8a5b647..af4e823 100644
--- a/src/dns_conf.c
+++ b/src/dns_conf.c
@@ -462,6 +462,7 @@ static int _config_server(int argc, char *argv[], dns_server_type_t type, int de
 	unsigned int result_flag = 0;
 	unsigned int server_flag = 0;
 	unsigned char *spki = NULL;
+	int drop_packet_latency_ms = 0;
 
 	int ttl = 0;
 	/* clang-format off */
@@ -472,6 +473,7 @@ static int _config_server(int argc, char *argv[], dns_server_type_t type, int de
 		/* experimental feature */
 		{"check-edns", no_argument, NULL, 'e'},   /* check edns */
 #endif 
+		{"drop-packet-latency", required_argument, NULL, 'D'},
 		{"spki-pin", required_argument, NULL, 'p'}, /* check SPKI pin */
 		{"host-name", required_argument, NULL, 'h'}, /* host name */
 		{"http-host", required_argument, NULL, 'H'}, /* http host */
@@ -503,6 +505,7 @@ static int _config_server(int argc, char *argv[], dns_server_type_t type, int de
 	server->tls_host_verify[0] = '\0';
 	server->proxyname[0] = '\0';
 	server->set_mark = -1;
+	server->drop_packet_latency_ms = drop_packet_latency_ms;
 
 	if (parse_uri(ip, scheme, server->server, &port, server->path) != 0) {
 		return -1;
@@ -572,6 +575,10 @@ static int _config_server(int argc, char *argv[], dns_server_type_t type, int de
 			safe_strncpy(server->httphost, optarg, DNS_MAX_CNAME_LEN);
 			break;
 		}
+		case 'D': {
+			drop_packet_latency_ms = atoi(optarg);
+			break;
+		}
 		case 'E': {
 			server_flag |= SERVER_FLAG_EXCLUDE_DEFAULT;
 			break;
@@ -618,6 +625,7 @@ static int _config_server(int argc, char *argv[], dns_server_type_t type, int de
 	server->result_flag = result_flag;
 	server->server_flag = server_flag;
 	server->ttl = ttl;
+	server->drop_packet_latency_ms = drop_packet_latency_ms;
 	dns_conf_server_num++;
 	tlog(TLOG_DEBUG, "add server %s, flag: %X, ttl: %d", ip, result_flag, ttl);
 
diff --git a/src/dns_conf.h b/src/dns_conf.h
index 586b60e..aefd83c 100644
--- a/src/dns_conf.h
+++ b/src/dns_conf.h
@@ -282,6 +282,7 @@ struct dns_servers {
 	int ttl;
 	dns_server_type_t type;
 	long long set_mark;
+	unsigned int drop_packet_latency_ms;
 	char skip_check_cert;
 	char spki[DNS_MAX_SPKI_LEN];
 	char hostname[DNS_MAX_CNAME_LEN];
diff --git a/src/smartdns.c b/src/smartdns.c
index 50fd995..d7c18f9 100644
--- a/src/smartdns.c
+++ b/src/smartdns.c
@@ -269,6 +269,7 @@ static int _smartdns_add_servers(void)
 		flags.server_flag = dns_conf_servers[i].server_flag;
 		flags.result_flag = dns_conf_servers[i].result_flag;
 		flags.set_mark = dns_conf_servers[i].set_mark;
+		flags.drop_packet_latency_ms = dns_conf_servers[i].drop_packet_latency_ms;
 		safe_strncpy(flags.proxyname, dns_conf_servers[i].proxyname, sizeof(flags.proxyname));
 		ret = dns_client_add_server(dns_conf_servers[i].server, dns_conf_servers[i].port, dns_conf_servers[i].type,
 									&flags);