rds-shared (PostgreSQL)

Creates a single RDS PostgreSQL instance intended to host multiple logical databases (e.g., one for dev, another for prod) to save cost.

What this module does

• DB subnet group (you pass the subnets)
• Security Group allowing inbound only from the SGs you specify
• (Optional) custom parameter group (e.g., rds.force_ssl = 1)
• RDS instance (PostgreSQL; single-AZ by default; gp3 storage; backups; deletion protection)
• Secret in AWS Secrets Manager for the master credentials + connection info

This module does not create logical databases or app users. Do that with:

• CI/CD migrations (preferred), or
• a separate Terraform step using the postgresql provider (requires network access to RDS via TFC Agent or running locally).

Inputs (key)

• Networking: vpc_id, db_subnet_ids, allowed_sg_ids
• Engine/size: engine_version, instance_class, allocated_storage, max_allocated_storage
• Ops: backup_retention_days, maintenance_window, backup_window, deletion_protection, multi_az
• Secrets: master_username (password auto-generated)
• Parameters: create_parameter_group, parameters (map of {name, value, apply_method})
• Tags

Outputs

• rds_endpoint, rds_address, rds_port
• db_instance_arn, db_instance_id
• db_subnet_group_name, rds_sg_id
• master_secret_arn

Example

module "rds_shared" {
  source = "./modules/rds-shared"

  name            = "shared"
  vpc_id          = var.vpc_id
  db_subnet_ids   = var.private_subnet_ids
  allowed_sg_ids  = [module.users_web_api.service_sg_id, module.email_web_api.service_sg_id]

  engine_version         = "16.6"
  instance_class         = "db.t4g.micro"
  allocated_storage      = 20
  max_allocated_storage  = 100
  backup_retention_days  = 7
  deletion_protection    = true

  tags = { Project = "EColors", Env = "shared" }
}

# Consume in services (example connection string in app config)
# host = module.rds_shared.rds_address
# port = module.rds_shared.rds_port
# username/password from Secrets Manager: module.rds_shared.master_secret_arn