Went through the senior SWE interview loop at Walgreens last quarter (their Chicago tech office, part of the Walgreens Boots Alliance tech org). Three rounds total but the system design piece felt like the real differentiator at the senior level.
The system design round was 60 minutes, one interviewer from their platform team. No shared doc, just a Lucidchart-style whiteboard link they sent ahead of time.
The prompt I got: Design a prescription refill notification system that handles 5M pharmacy customers across SMS, push, and email channels with delivery guarantees and personalization.
I opened with clarifications (delivery guarantees: at-least-once? exactly-once? what's the SLA for a missed notification?). The interviewer was engaged and didn't want me to just dive into boxes-and-arrows. Good sign.
Key things they cared about: Queue architecture. I went with Kafka and walked through partition strategy. They probed on what happens when a consumer group falls behind. Idempotency. Prescription notifications can't be sent twice (this is a regulated use case for them). They pushed hard on how I'd handle duplicate delivery. Observability. They literally asked "how would your on-call team know something is wrong at 2am without paging for false positives." Wanted to hear about alerting strategy, not just "we add metrics." Multi-channel fan-out. The design for handling SMS vs email vs push separately or in one service. I split them; they seemed to prefer that.
Things I didn't get pushed on much: specific database choices, caching layer details. They cared more about correctness and resilience than performance optimization.
For senior (their equivalent of what other companies might call L5 or IC4 depending on your reference frame), the bar felt like: can you drive the design, handle pushback gracefully, and show you've thought about operational concerns, not just the happy path.
I got an offer. Total comp for senior SWE was around 155-165 all-in (base + annual bonus), which is below FAANG but on the high end for what I'd expect from a large retailer in this market. Team seemed solid. Lots of modernization work happening on the pharmacy platform side.