This was for Office 365 team. Was invited to attend a whole day interview at their campus in Hyderabad. Went in at 9 AM, came out by 5 PM. Was interviewed by 4 interviewers, all of them from office team only. Could sense they are all very knowledgeable and pretty senior. Each of them was very courteous and took good amount of time analyzing my expertise on the specific area they were interviewing on. First round was problem solving and the interviewer, a senior engineer, was very specific on the code written, the edge cases, the readability, and extensibility of the code. Would check how I would extend the code for a more generic problem. Some brushing up on design patterns would help here. Took around 45 minutes. Second round was a mix of low level design, data structures and algorithms, and high level design. Interviewer was a mid level engineer, very friendly, and this round went more or less like a friendly discussion. Ended with a datastructure problem, where I was asked to write code on paper. Took about 1 hr. Third round was mostly high level design. Took by an ex googler and principal engineer here, too brilliant! Dug very deep into the intricacies of designing the system for the given problem. This round actually sealed it for me that I need to join this team. took around 1 hr. Fourth and final round was probably with the hiring manager. Again very technical interview, on various aspects ranging from ds, algo, low level design, high level design. He took more time than the others.