Parallel Processing with Scala Future's Eager Evaluation and Applicative Functor

In microservice architectures, sequential integration using Future's flatMap when calling multiple APIs causes performance degradation because each call waits until completion. Scala's default Future supports eager evaluation, meaning it executes immediately upon declaration. Cats' Future instance internally uses flatMap to implement ap, but thanks to eager evaluation, it can achieve parallel behavior by combining the results of Futures that are already running during product or mapN operations. In contrast, Scalaz and Monix provide Nondeterminism functionality, allowing explicit selection of whether to compute Applicative in parallel or sequentially. This enables running independent Futures in parallel and combining their results to reduce response time.