The typical interview process at Microsoft Ireland is as follows:

• CV screening/filtering (I estimate that 90% of applications are rejected at this stage).
• Coding puzzle (solution to be sent within 1 hour).
• Initial phone screen (HR plus simple technical questions).
• One or two technical phone interviews (with engineers).
• On-site interview.

Somehow, I did not have to complete the first coding puzzle. This was likely because I was recommended by another Microsoft employee (based in the US), so they initially assumed I was applying for a job in the US. Once clarified, they passed my CV to the Irish recruiters, who moved me directly to the phone screening stage. It's probably best to get recommended to bypass some initial filters.

The phone screens were quite typical:

• Short technical questions covering OOP, programming languages, databases, and networks (5-10 minutes).
• Design question (15 minutes).
• Coding question (typically related to the design from the previous step - 20 minutes).
• Discussion of the coding solution (how to improve it, how to test it, what test methodologies to use - 10 minutes).
• Q&A (this is when you can ask your questions).

The on-site interview consisted of four 1:1 interviews (45 minutes each, with a 15-minute break) with multiple engineers. Some interviews focused on design skills, some on coding (on a whiteboard), and some on testing. Everyone asked some short, random questions about algorithms, data structures, programming languages, network protocols, etc.

The final hour (only 2 out of 10 people reached this stage when I was interviewed) was with the director of the department to which I was applying. It was extremely challenging! I was asked about network protocols and data structures, and I was given an algorithmic problem to solve (similar to the "egg dropping problem"). I had to figure out the optimal, not just any, algorithm and provide a formal mathematical proof of its complexity (big O notation).

The last 1-hour interview on-site was the most difficult (described in the interview process above).