Envoy·Software Engineer·Onsite - System Design / Architecture
Apr 2026
System design round at Envoy for a software engineering role. The prompt was a shopping cart implementation, which sounds boring until you realize how many rabbit holes it opens up. Spent most of the time debating my own design decisions out loud, which felt awkward but seemed to be the point.
- Design and implement a Shopping Cart system that supports adding/updating/removing items, computing subtotals, applying multiple coupon types, computing tax by state, and locking the cart after checkout so further mutations throw an error.
“The spec was intentionally left vague, which I did not fully appreciate until I was ten minutes in and already committed to a design that had no coupon precedence rules.” The rest of the author's notes on Software Engineer interview at Envoy, Onsite - System Design / Architecture round, covers how they worked through the question, what the panel pushed back on, and what they would do differently.
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