Finished my Datadog SRE loop about 5 weeks ago. Sharing because I found basically nothing useful when I was prepping.
The loop was 5 rounds virtual: coding screen, then four back-to-back sessions on a single day. Sessions were: a coding round (medium leetcode, nothing crazy), a system design round, a "debugging" round, and a behavioral. There was also a short intro call with the hiring manager.
The debugging round is the one nobody talks about. They gave me a simulated scenario: a service with degraded throughput, and I had access to what was supposed to look like a simplified Datadog UI with metrics, logs, and traces. I had to walk through what I'd check and why. Not memorizable. You have to actually know how you investigate production issues. I kept narrating my reasoning and I think that's what saved me. Silence is bad in that round.
System design was infra-flavored. Not "design Twitter." More like "how would you build a metrics ingestion pipeline that handles spikes without dropping data." Really specific to what Datadog actually does. Expect tradeoffs around cardinality and write throughput.
Behavioral was low-key but they probed on incident response stories specifically. "Tell me about a time a system you owned had an unexpected failure" came up. Have a real story, not a polished one.
One thing that caught me off guard: the interviewers were really senior. Like, principal+ level engineers in the room. They can tell when you're pattern-matching to a rehearsed answer. Just be direct.