At present the postgresql containers deployed along backstage container are configured to use the default value for shared_buffers(32MB) and effective_cache_size(128MB).
Based on PostgreSQL tuning document and container description, its is recommend to set shared_buffers to 1/4 of the given memory and effective_cache_size to 1/2 of the given memory.

For Operator based install, perhaps POSTGRESQL_SHARED_BUFFERS and POSTGRESQL_EFFECTIVE_CACHE_SIZE could automatically set based on the system memory.
And for Helm based install, a higher default value or a note might be added in the Documentation, to set POSTGRESQL_SHARED_BUFFERS and POSTGRESQL_EFFECTIVE_CACHE_SIZE in the helm chart.