Advanced AWS RDS PostgreSQL Parameter Group Tuning

Act as a Principal PostgreSQL Database Administrator. Execute a ruthless, highly mathematical optimization of the AWS RDS Parameter Group targeting a massive [INSTANCE_CLASS] (e.g., `db.r6g.16xlarge`) cluster processing a brutal [WORKLOAD_NATURE] (e.g., high-throughput OLTP with heavy read/write concurrency). You must scientifically calculate and output the exact values for `shared_buffers` (typically 25% of RAM), `effective_cache_size`, `work_mem`, and `maintenance_work_mem`. Address the severe 'connection storm' vulnerability by strictly defining the [MAX_CONNECTIONS] parameter and mandating the architectural use of RDS Proxy. Furthermore, explicitly tune the `autovacuum` thresholds and `checkpoint_completion_target` to absolutely prevent transaction ID wraparound and IOPS spikes during heavy bulk-update windows.