Demo case file · System design
Site Reliability Engineer
This is a demo case file: a realistic example written from commonly known interview formats, not a real candidate's interview experience.
Questions asked
- Design a system that collects and aggregates logs from 10,000 servers across three data centers, and estimate how many machines, how much disk and how much network bandwidth it needs.
- One of the three data centers goes offline. Walk through how your design behaves and what the people querying logs would notice.
- What SLOs would you set for this system, and what would you page someone for versus fix during working hours?
What to expect
A "non-abstract" design round — boxes and arrows weren't enough. The interviewer wanted concrete numbers: bytes per log line, lines per second per server, disks per machine, and a rough total cost. Kept asking what happens when each component fails, and was happy for me to use round numbers as long as I did the math out loud.
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