All of the RAM is eaten by zabbix_server process, responsible for SNMP Traps.

Zabbix stats:
Parameter Value Details
Zabbix server is running Yes localhost:10051
Number of hosts (monitored/not monitored/templates) 25 2 / 0 / 23
Number of items (monitored/disabled/not supported) 2776 2772 / 0 / 4
Number of triggers (enabled/disabled)[problem/unknown/ok] 43 43 / 0 [0 / 0 / 43]
Number of users (online) 9 2
Required server performance, new values per second 464.38 -

I use Zabbix for processing of SNMP traps received from CISCO DCM9900. I have created few hundreds of regular expressions, identifying source service contained in snmp trap.

I use mainly computed items, which uses stored regular expressions and contains formulas like:
count("DCM:snmptrap[\"@Rai_3_out\"]",5,"CC Error","like",10)

Graph of free emmory is included. You can see piked as i have restarted zabbix server.