went through the microsoft onsite in february for a senior backend role on the Azure org. sharing the full picture because the 'microsoft final round' content out there is pretty vague.
format for L63 senior SWE: 5 rounds total. all virtual (they've kept this since covid for most roles, though some teams are back to in-person in Redmond for certain positions). round 1: coding (live, 55 min) round 2: system design (55 min) round 3: behavioral (50 min) round 4: coding OR a second behavioral, depends on team (55 min) round 5: 'as appropriate' round, sometimes with a hiring manager
my specific schedule had rounds 1-4 back to back with one 30-minute break in between. it's a long day. eat a real meal before it starts.
what i noticed about the interviewers: they brief before each round and immediately tell you what they're focused on. this is different from google or meta where you kind of figure it out. microsoft interviewers literally said 'i'm going to focus on problem solving and communication today.' they're generally collegial. not friendly-to-a-fault like some apple interviewers i've had, but not intimidating. each interviewer submits their score independently. there's no group debrief until after all scores are in.
the debrief / decision timeline: recruiter called me 5 business days after the onsite. she said the 'as appropriate' round occasionally adds time but for me it was under a week. offer came the same call as the decision, which is unusual but apparently not unheard of.
leveling: big topic for microsoft. they do recalibrate you during the loop. if you're targeting L63 but perform at L64 level, some teams will upgrade. i've heard the reverse happens too. if you care about level, ask the recruiter how leveling decisions get made before your loop.
overall: process felt respectful of my time. no silly brain teasers. the hardest part was honestly the behavioral round because they went deep on a couple of stories.