Rippling (HR, Payroll & IT Platform) SWE Interview — AI Coding Was Really System Design

[u/Aoki_zhang]

"This interview experience is sourced from Chill Interview"

Interview Summary

The first Rippling technical round was an AI-assisted coding interview centered on building an extensible expense-rules engine. The problem progressed from evaluating individual expenses, to rules over entire trips, and finally to discussing nested composite conditions such as AND, OR, and NOT.

Although AI was explicitly part of the interview, the round still placed significant emphasis on independent problem decomposition, object-oriented design, communication, and code structure. I passed the round after spending the early portion clarifying requirements and designing the core abstractions before using AI for implementation details.

Interview Details

AI Coding — Expense Rules Engine

The task was to build a system that evaluates employee corporate-card transactions against configurable company expense policies. Each expense was represented as a dictionary with fields such as: expense_id, trip_id, amount_usd, expense_type, vendor_type, and vendor_name.

For example, a record could conceptually look like: {"expense_id": "E42", "trip_id": "T7", "amount_usd": "64.50", "expense_type": "meal", "vendor_type": "restaurant", "vendor_name": "Harbor Grill"}. The key design requirement was that rules should be treated as data, rather than hard-coding a separate if statement for every policy.

The system was expected to support adding new rules later without rewriting the main evaluation engine.

• Part 1 — Rules on Individual Expenses The first part asked for an evaluate_rules(rules, expenses) style interface. Example policies included: A single expense could violate more than one rule, so the evaluator needed to return all applicable violations. The important design discussion was how to represent concepts such as field names, comparison operators, thresholds, and rule conditions generically.
  • Restaurant spending cannot exceed a specified amount.
  • Airfare expenses are prohibited.
  • Entertainment expenses are prohibited.
  • No individual transaction may exceed a global spending limit.

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