When you make a call to any REST endpoint and if any issue pops up, it is difficult to trace the issue and its root origin because each call is made to a server, and this call may call another, and so on and so forth. This makes it very difficult to figure out how one particular request was transformed and what it was called. Normally, an issue that is caused by one service can have domino effect on other services or can fail other service operation. It is very difficult to track and may require an enormous amount of effort. If it is monolithic, you know that you are looking in the right direction, but microservices make it difficult to understand what the source of the issue is and where you should get your data.