AWS Aurora running out of freeable memory and crashing
Rate Per Second=RPS - Suggestions to consider for your AWS Aurora Parameters Group

log_output=TABLE,FILE  # from TABLE so you can review your Error Log FILE after crash
log_warnings=2  # from 1 to include aborted_connects and other info in your Error Log
query_cache_min_res_unit=512  # from 4096 to conserve QC RAM used
query_cache_size=64M  # from ~ 443M to reduce CPU cycles used for QC management
innodb_lru_scan_depth=100  # from 1024 to conserve 90% CPU cycles used for function
thread_cache_size=24  # from 11 to reduce threads_created count
read_rnd_buffer_size=256K  # from 512K to reduce Handler_read_rnd_next RPS of 2,558
read_buffer_size=512K  # from 256K to reduce Handler_read_next RPS of 29,608
tmp_table_size=64M  # from 16M to expand capacity
max_heap_table_size=64M  # from 16M to reduce created_tmp_disk_tables RPHr of 1,134


if ALLOWED,

innodb_io_capacity=1900  # from 200 to enable higher IOPS to SSD devices


OBSERVATIONS,
innodb_buffer_pool_size adjustment to be considered when innodb_buffer_pool_reads > 50 RPS (you are less than 1 RPS today)
innodb_change_buffering=none    to be reconsidered, review refman details

These Suggestions may help stabilize your instance.

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