How would you scale rule evaluation?
Company: Rippling
Role: Software Engineer
Category: System Design
Difficulty: easy
Interview Round: Technical Screen
Assume the same expense-policy rule engine must now support up to 1,000,000 active rules and efficiently evaluate batches of around 1,000 expense records.
Discuss how you would design the system so that it scales in practice. Your answer should cover:
- how rules are stored and represented;
- how to avoid scanning every rule for every expense;
- how grouped rules are evaluated efficiently;
- batching, indexing, and partitioning strategies;
- how rule updates are propagated safely;
- key latency, throughput, and reliability considerations.
Quick Answer: This System Design question evaluates a candidate's ability to design a scalable rule-evaluation system, testing competencies in distributed systems, rule engines, performance engineering, data indexing and partitioning, batching, and safe state propagation for high-throughput, low-latency workloads.