Every microservice inside the infrastructure is made to handle a certain set of requests. As the number of requests to the application increases, some of the microservices may see an increased load on them in comparison to the other services.

Imagine there is an e-commerce website that is based upon the microservices architecture. There is a flash sale going on, and a lot of customers are trying to checkout and pay for their purchase at the same time. If the services that handle the checkout and payment for the customers does not scale up during the increased load, the customers may face increased response times or timeouts, creating chaos for the e-commerce company, whose customer care might now be busy in dealing with the angry customers.

The scalability testing of microservices aims to test that a service is able to scale up and scale down as the load varies, so as to keep the response times adequate, and to properly handle the varied loads during its life cycle.

Now, we have the knowledge of the different kinds of testing that needs to happen for a microservices based application. But what are some the challenges that make this testing a challenging task to achieve? Let's try to go through the challenges one by one and see if there is something we can do about them.