Blocking and low performance. Due to the synchronous nature of HTTP, the original request doesn't get a response until all the internal HTTP calls are finished. Imagine if the number of these calls increases significantly and at the same time one of the intermediate HTTP calls to a microservice is blocked. The result is that performance is impacted, and the overall scalability will be exponentially affected as additional HTTP requests increase.

Coupling microservices with HTTP. Business microservices shouldn't be coupled with other business microservices. Ideally, they shouldn't "know" about the existence of other microservices. If your application relies on coupling microservices as in the example, achieving autonomy per microservice will be almost impossible.

Failure in any one microservice. If you implemented a chain of microservices linked by HTTP calls, when any of the 

https://learn.microsoft.com/en-us/dotnet/architecture/microservices/architect-microservice-container-applications/distributed-data-management