Went through the full Allstate loop for a Senior SWE role (Northbrook, IL, remote-eligible) earlier this month. Wanted to write up the system design round while it's fresh because there isn't much out there that's specific.
First: Allstate doesn't use L-numbers publicly but internally maps to a band. The level I was interviewing for translates roughly to what other companies call L5 or Senior IC. The recruiter confirmed "senior contributor" when I asked.
The system design round itself
One hour, two interviewers, one from the team I'd be joining and one from a neighboring platform team. They gave me a prompt about five minutes in: design a real-time claims-status notification system. The framing was clearly insurance-domain, which makes sense. You don't need insurance knowledge per se but being able to talk through event-driven architecture in a regulated, high-volume environment matters.
Things that came up: How do you handle 10-15 million active policies each generating state updates during a storm event (think CAT loss scenarios) Kafka vs. something simpler. They pushed on throughput vs. latency tradeoffs. Data persistence layer: they were interested in whether I'd choose SQL or NoSQL and why. I went with Postgres for the core claims ledger (audit trail, compliance) and Redis for hot read-through on status. That landed well. Notification fanout: push vs. poll, mobile vs. email. They asked about idempotency explicitly.
About 40 minutes of diagramming (I shared screen, they didn't use a whiteboard tool, just me drawing in Excalidraw) then 15-20 minutes of Q&A and deep dives.
No Leetcode in this round. Pure system design.
What they seemed to care about
Compliance came up twice. Allstate is a heavily regulated company and they want to see that you understand what that means for data residency, audit logging, and rollback capability. If you've worked in fintech or healthcare you'll feel at home. If you haven't, spend five minutes thinking about what it means to design a system where every state transition has to be auditable.
Overall difficulty: not harder than a solid tech company senior round. If you can do Google L4-L5 system design, this is comparable. The insurance framing is the main wrinkle.
Happy to answer specifics if you're prepping.