A national university has launched its serverless online learning portal using AWS Lambda and API Gateway in AWS that enables its students to enroll, see grades online as well as manage the class schedule. The portal abruptly stopped working after a few weeks and lost all of its data. The university hired a DevOps consultant and based on the investigation, the outage was due to an SQL injection vulnerability on the portal's login page in which the attacker simply injected the malicious SQL code. The consultant also emphasized the system's inability to track historical changes to the rules and metrics associated with its firewall. Which of the following is the MOST suitable and cost-effective solution to avoid another SQL Injection attack against the infrastructure in AWS?