Which of the following is a cost effective way to improve application performance?

Explanations:

While upgrading to t2.xlarge instances may provide more CPU and memory resources, it does not address the network constraints directly and may not be cost-effective compared to other options.

Using AWS Auto Scaling with m4.large instances for the web and application tiers allows for dynamic scaling based on demand, improving performance during peak times and efficiently utilizing resources at lower times, thus being cost-effective.

Converting to a self-managed MySQL cluster increases management overhead and complexity, which may not be cost-effective and does not directly address the performance issues in the web and application tiers.

Creating an Amazon CloudFront distribution to cache content can significantly reduce load on the web servers by serving cached static content to users, improving performance and scalability, particularly during peak times.

Increasing the size of the RDS instance to db.m4.xlarge may improve database performance but does not address the network constraints experienced in the web and application tiers, making it less effective as a standalone solution.