The first thing that you have to understand is that MongoDB is trying to find the "best of the best". Therefore the interview goes into disqualification mode. Another interesting thing is that even when this is a "database" product, that doesn't mean that they are looking for people with database skills, my impression is that they would take anyone with strong Linux and storage background. In addition, every interview is different and as matter of fact they track every single question into their system and hence they know exactly what they have asked and what needs to be asked in the next interview. Questions in my first phone interview: - What is an index? - What are the benefits/downsides of an index? - What is a compound index? - How to resolve the Intersection of the list? In a database world, this is the equivalent of a join. The easy answer would be a nested loop. - Questions about raids. (Rad 1, Raid 5, Raid 10). - Other types of db questions like What is a correlated query? Second phone interview: - What is a virtual function? - What is a template? - How do you implement virtual functions in C? - Scenario Question: I have deployed a new application and it has performance issues, how do I troubleshoot it? - Scenario Question: What happens when you submit a query to the database? (query parsing process) First onsite interview. - The interview was a web meeting and it was 2 person panel. In this interview both guys are asking questions at the same time. - Scenario questions: We have 2 systems, everything is the same, one system is performing fine and the other is executing queries slower, how do you approach this problem? - How do you change kernel parameters? - Can you explain in detail how swap space work? - What happen if you have an application of 8 GB and you only have 4GB of physical memory? - Provide an example of one of the most complex issues you have resolved. Second onsite interview: - What information is need in order to configure the network settings in a computer? - What is TCP? - What is UDP? - Provide examples of applications using UDP / TCP - Questions about network services like DHCP, DNS. - Utilities to monitor performance in Linux. - Explain RAIDs. - If you have RAID 5, how much space can be actually used? Does it change if you add more disks? - What utilities do you use to monitor performance of the operating system? - Scenario question: How do you troubleshoot a connection issue between an application and a database server? Third onsite interview: This guy only asked one question: "Can you design a system to store a PB of information?" You have to put attention to the following components: - What type of HW are you going to use? - How are you going to store the actual data? - Details about cluster configuration, what if the heartbeat fails but it is a false positive? - Do you replicate the information? how? and how long would it take if one node fails? - Be ready to do quick calculations. For instance, if you said you have an internal network of 1 Gbit per second, how long would it take to transfer 1 TB? - The solution has to be designed in a way that it can grown in a horizontal way. Tips: - You have to convince the interviewer that you want to work for Mongodb because you really like the technology and not just because it is a nice company. - The interviewer also expects some type of level of knowledge about MongoDB and how it is been used by the customers. - Your answer has to be complete, give as much detail as possible. - You have to know what you are responding. For instance, if you said "You can use vmstat to monitor cpu, memory and swap space", a follow-up question would be "Can you tell me what information vmstat is giving you about the swap space? is it in pages, blocks or MB? - Google known issues with MongoDB and Linux. They can be used as example in your answers.