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Waymo·Software Engineer·Onsite - System Design / Architecture·Senior

SeniorPrefer not to say
May 2026

Summary

Waymo system design round, one big open-ended question that basically asked me to design a whole evaluation-as-a-service platform from scratch. Dense problem with a lot of moving parts and I'm not sure I covered everything they wanted.

Questions Asked (1)

Q1

Design an evaluation platform that supports both human reviewers and LLM-based judges, covering task ingestion and routing, evaluator pool management, quality control mechanisms, consensus aggregation, throughput and SLA guarantees, cost trade-offs, and customer-facing APIs.

System DesignTechnical Trade-offsAPI & Integrations
Author's notes

This question is basically six questions stapled together.

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AI HintsAI Generated

Suggested Approach

Start by clarifying requirements and scale, then propose a modular architecture with separate services for task ingestion, routing, evaluator management, and aggregation. Walk through each component, emphasizing trade-offs between human and LLM evaluators, and conclude with API design and SLA considerations.

Pro tip: Emphasize the importance of a feedback loop where LLM judgments are periodically validated against human reviews to maintain quality and reduce cost over time.

1. Clarify Requirements and Scale

Ask questions to understand expected throughput, latency SLAs, cost constraints, and the mix of human vs. LLM evaluators. This informs architectural decisions.

2. Design Core Components

Outline services for task ingestion (APIs, queues), routing (based on task type, cost, availability), evaluator pool management (registration, skills, availability), and consensus aggregation (voting, weighted scores).

3. Address Quality Control and Consensus

Describe mechanisms like gold-standard tasks, inter-rater reliability, and LLM confidence scores to ensure quality. Explain aggregation methods (majority vote, average, weighted) and conflict resolution.

4. Ensure Throughput and SLA Guarantees

Discuss scaling strategies (horizontal scaling, auto-scaling), prioritization queues, and fallback mechanisms (e.g., switch to LLM if human pool is saturated) to meet SLAs.

5. Define Customer-Facing APIs and Cost Trade-offs

Propose RESTful APIs for task submission, status checks, and result retrieval. Discuss cost optimization by routing simple tasks to LLMs and complex ones to humans, and caching results.

Key Points to Mention

  • Task routing logic based on complexity, cost, and evaluator availability
  • Evaluator pool management: skills, reputation, and dynamic pricing for human reviewers
  • Quality control: gold tasks, inter-rater reliability, and LLM validation against human reviews
  • Consensus aggregation: weighted voting, confidence scores, and conflict resolution
  • SLA guarantees: prioritization, auto-scaling, and fallback to LLM judges
  • Cost trade-offs: LLM vs. human cost, caching, and batching

AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.