Its regarding collection of traffic flows of ntopng.
I tried every thing to overcome with this problem :

1.tried to collect the data in mysql database , but problem is that i can't read those tables coz they are fully encrypted moreover it's only be readable through ntop ( paid version)

2- I tried to collect the data in nprobe but with in 30 minutes its used about 4GB space of my disk , means its sending PCAP data which is unusable for me coz I want flows so that I can see the URLS also.

3- other than ntop I also treid like zabbix and Ngios but no one work like Ntopng.

At last I tried every thing and researched about every possibilities but every time my question remain same ... Is it possible to store historical flow and can we see those ???