pdns FE crash when stressed QPS

[Sephiroth80]

Hi everybody i ask to the community how can i made to my FE can't crash when i stressed sending from outside QPS, i let my PDNS conf and my SQL conf, i was tried some modifications but was useless
pdns.conf
allow-notify-from=xx.xxx.xxx.xxx (backend ip)
allow-unsigned-autoprimary=yes
allow-unsigned-supermaster=yes
any-to-tcp=yes
autosecondary=yes
disable-axfr=no
launch=gmysql
gmysql-host=localhost
gmysql-user=xxxxx
gmysql-password=xxxxxx
gmysql-dbname=xxxxxx
local-address=0.0.0.0, ::
local-port=53
loglevel=6
master=no
primary=no
query-local-address=0.0.0.0 ::
setgid=pdns
setuid=pdns
slave=yes
slave-cycle-interval=10
slave-renotify=yes
superslave=yes
webserver=yes
webserver-address=xx.xxx.xxx.xxx (local ip)
webserver-loglevel=none
webserver-allow-from=0.0.0.0/0,::/0

mariadb-server.cnf
[mysqld]
datadir=/var/lib/mysql
socket=/var/lib/mysql/mysql.sock
log-error=/var/log/mariadb/mariadb.log
pid-file=/run/mariadb/mariadb.pid

In mariadb-server.conf i was try the next config
[mysqld]
innodb_buffer_pool_size = 8G
innodb_log_file_size = 256M
innodb_flush_log_at_trx_commit = 2
max_connections = 1000
query_cache_type = 1
query_cache_size = 128M
table_open_cache = 1024
tmp_table_size = 64M
max_heap_table_size = 64M
thread_cache_size = 64

and in pdns.conf
gmysql-dnssec=no
cache-ttl=300
negquery-cache-ttl=60
query-cache-ttl=300

but this config was worth, so i really need some help

thanks a lot