Hello friends,

This is a mock system design interview in which I have asked the candidate to design file storage service like DropBox. This mock system design interview is an excellent example of showing you that in how much detail and depth an interviewer can go to evaluate the candidate for the senior/principal engineering position. This mock system design interview also shows that how much it is important that you should do due consideration when discussing functional and non-functional requirements and make sure that your later design then adhere to the functional and non-functional requirements that you have discussed with the interviewer. If you later try to design the system in a way that is not adhering to the requirements that you have discussed then an experienced interviewer can easily point that out.