Choosing the best Design Pattern

I am planning to create a link-shortening service. I am using MERN and Redis for caching db. I am still thinking about a design pattern that I should use for it. I am trying some approaches.

1. Create a full monolithic app, including all the front-end, user management, link management, and link-clicking mechanism
2. Create a microservice for the link clicking and another for other all tasks.

What would be most cost-effective, I am hoping to get ~100,000 clicks per month. When choosing a hosting service, what should I choose?

I want to deploy this on AWS. If we choose 1st approach what would be the most suitable service, with a minimum budget? and if not for other approch