Microservices that are well designed are highly scalable, but it does mean having infinite resources. With cloud-computer-limited resources, it is very relative, but the cost to provide a service can become so high that it prevents the same.
Thinking about it, some steps can be taken to reduce the cost of consumption. One, as mentioned earlier, is the implementation of an efficient cache. However, that's not all; at times, throttling is necessary to block the high consumption of resources.
It is not feasible that a client of a microservice as a web page runs a very high number of requests for the microservice, or that the same page is not mature enough to handle data already received.
For this, simple throttling that keeps the reference of who consumes the information and the data transferred to the client is very effective for reducing the consumption of microservices.
Some throttling policies can be applied:
Number of requests per minute from the same client
Number of requests per second from the same client
Number of requests per minute from the same client for similar information
Number of requests per second for the same client for the same information
With these, it is possible to limit such potential blunders as inadequate data manipulation, irresponsible Ajax requests, and less sophisticated attack attempts.