Finally got through the Mars Inc. software engineering loop a few months ago. Sharing the full thing because I couldn't find much recent info when I was prepping.
Background: I applied for a mid-senior backend role on their digital technology team. Mars has been doing a quiet but real tech buildout, mostly focused on supply chain systems, e-commerce integrations, and internal tooling for their global brands (Snickers, M&M's, Pedigree, etc.).
Timeline Application submitted online. About 10 days later a recruiter reached out via LinkedIn. First call was 20 minutes. Then they scheduled a technical phone screen. Offer came roughly 5 weeks from first contact.
Rounds Recruiter screen (20 min, values-heavy, logistics) Technical phone screen with a Mars engineer (45 min, coding + quick design chat) Take-home assessment. Wasn't super hard, but it wasn't trivial either. I'd call it LeetCode medium territory but structured as a real-world problem involving data transformation. 3 days to complete. Full onsite loop (virtual in my case). Three back-to-back sessions: one coding, one system design, one behavioral/values. About 3.5 hours total.
What surprised me Mars is not a FAANG-style shop. The system design round was not about massive scale. They care a lot about pragmatic, maintainable solutions. When I started overengineering a cache layer the interviewer literally said "what problem does that solve for us today?" and that recalibration mattered.
The coding round was two problems. Both were applied problems, not abstract puzzles. Think: given this dataset of orders, transform and aggregate for reporting. Not graph theory.
Decision came 6 business days after the final onsite. No ghosting, which was refreshing.
Happy to answer specific questions. It's not a household name for tech jobs but the process was actually pretty humane.