InfluxDB 2 -- OOM

Hello, I am new to InfluxDB and started working with this 4 days ago, Initially i installed 1.8 version but later upgraded to v2.0.
I am treating this as an out of the box approach now, I was able to setup the insertion into influx using GitHub - influxdata/influxdb-client-php: InfluxDB (v2+) Client Library for PHP and batch of 5000 with a timeout of 30 seconds.
I have created 2 buckets with 24 hour retention period, one for 15 minute interval data and one for 16 minute interval data. This insertion rate is approx. 21 Million per hour.
There is no other queries running on the server for now.
I have not taken cardinality into account yet, i was trying to go down - implement first and optimize later path and was expecting the ingestion to be running slow but not crashing.
Following is a snapshot for htop on the VM showing the resource utilization by InfluxDB. It is continuously using a lot of RAM and was killed by OOM Killer after 6 hours of runtime.

Any Help and advise is greatly appreciated, Thanks