To improve aws_s3.table_import_from_s3 performance, start by optimizing database parameters - set maintenance_work_mem to 1GB, increase max_wal_size to 4GB, and set checkpoint_timeout to 30 minutes. Drop indexes and foreign keys before import and recreate them after loading completes. Ensure the S3 bucket and RDS instance are in the same region and Availability Zone to minimize network latency. Consider using an S3 VPC endpoint for private connectivity. Monitor and tune ReadIOPS metrics using CloudWatch to verify if your working set fits in memory. For parallel loading, you can run multiple psql commands simultaneously to utilize available CPU cores effectively. However, be aware that increasing max_wal_size and checkpoint_timeout could extend recovery time to 10+ minutes in case of failover.