Correct. We tune overcommit so postgres reliably returns out of memory. It becomes complicated to accurately tune overcommit for every AWS instance type. We configure GOMEMLIMIT/cgroups but those are about RSS. Outliers come together: instances running queries out of memory on our service tend to also be pushing other resource limits, causing wal-g & prometheus exporters to start having more erratic memory usage at the worst time

This helps on both ends of the cost spectrum. Large 64 core instances are where our heuristics fall off the most as variance increases, & tiny instances with 8GB of memory can use every 100MB of RSS we can get