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

SeniorPrefer not to say
Jun 2026

Summary

System design round at Anthropic for a software engineer role, except it wasn't really a typical system design round. No whiteboard, no diagrams, just a Google Doc and a conversation that kept looping back on itself every time I thought I'd landed somewhere solid.

Questions Asked (3)

Q1

Design a 'Prompt Playground': a tool that lets users write, test, and iterate on prompts for large language models. Walk through the full product and system design.

System DesignProduct Sense & IdeationTechnical Trade-offs
Author's notes

I kept defaulting to backend-first thinking and the interviewer had to nudge me back to the UX side multiple times.

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AI HintsAI Generated

Suggested Approach

Start by clarifying requirements and scope with the interviewer, then structure your answer around user personas, core features, and system architecture. Emphasize trade-offs, scalability, and how you would measure success, while keeping the design iterative and user-centric.

Pro tip: Focus on the iteration loop—how users can quickly test, compare, and refine prompts—and discuss how you'd handle versioning and collaboration, as these are often overlooked but critical for real-world adoption.

1. Clarify Requirements and Scope

Ask questions to understand target users, key use cases, and constraints (e.g., model types, latency, cost). Define what 'prompt playground' means for this context.

2. Define Core Features and User Flow

Outline essential features: prompt editor, model selection, parameter tuning, test input/output, version history, and collaboration. Sketch the user journey from writing to iterating.

3. Design System Architecture

Propose a high-level architecture: frontend, backend API, LLM integration, storage for prompts/results, and caching. Discuss scalability, latency, and cost considerations.

4. Address Trade-offs and Challenges

Identify key trade-offs (e.g., real-time vs. batch testing, feature richness vs. simplicity) and challenges (e.g., prompt versioning, evaluation metrics, security).

5. Define Success Metrics and Future Extensions

Suggest metrics (e.g., iteration speed, user retention) and potential extensions (e.g., A/B testing, automated prompt optimization, team workspaces).

Key Points to Mention

  • Prompt versioning and diffing to track changes and compare performance
  • Integration with multiple LLMs and handling API rate limits/costs
  • Real-time collaboration features like commenting and sharing
  • Evaluation and scoring mechanisms for prompt outputs (e.g., human feedback, automated metrics)
  • Caching and optimization strategies to reduce latency and cost
  • Security and privacy considerations for user data and prompts

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

Q2

How would you handle very large prompts in the playground, specifically around context window limits, diffing between versions, and avoiding full re-runs when only part of the prompt changes?

System DesignTechnical Trade-offsAPI & Integrations
Author's notes

This is where I fumbled most.

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AI HintsAI Generated

Suggested Approach

Start by framing the problem as a system design challenge: managing large prompts within context window limits, efficiently diffing versions, and minimizing re-runs. Then, walk through a layered solution that includes prompt segmentation, caching, and incremental execution, emphasizing trade-offs between accuracy, cost, and latency.

Pro tip: Highlight that Anthropic's API supports prompt caching, which can drastically reduce cost and latency for repeated prefixes—this shows you understand the platform's capabilities and can leverage them for efficient large-prompt handling.

1. Clarify requirements and constraints

Ask about the typical prompt size, frequency of changes, and acceptable latency/cost. This ensures your solution is tailored to the actual use case.

2. Handle context window limits

Propose strategies like prompt truncation, summarization, or chunking with retrieval-augmented generation (RAG) to fit within limits while preserving essential information.

3. Implement efficient diffing

Use a diff algorithm (e.g., Myers diff) to identify changed segments at a granular level, enabling precise updates without reprocessing the entire prompt.

4. Avoid full re-runs with caching and incremental execution

Leverage prompt caching for unchanged prefixes and design a system that only re-executes the modified portions, stitching together cached and new results.

5. Discuss trade-offs and validation

Acknowledge potential issues like cache invalidation, consistency, and added complexity, and suggest validation mechanisms to ensure correctness.

Key Points to Mention

  • Context window limits: token counting, truncation, summarization, and chunking strategies.
  • Prompt caching: how it works and its benefits for repeated prefixes.
  • Diffing algorithms: line-based vs. semantic diffing, and handling structural changes.
  • Incremental execution: partial re-runs, dependency tracking, and result merging.
  • Trade-offs: cost vs. latency vs. accuracy, and complexity of implementation.
  • Anthropic-specific features: prompt caching API, token counting endpoints, and best practices.

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

Q3

How would you design the backend to store prompts, run histories, evaluation results, and per-user data at scale?

System DesignData Modeling
Author's notes

This part felt more comfortable.

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AI HintsAI Generated

Suggested Approach

Start by clarifying requirements and scale, then propose a high-level architecture that separates concerns: a relational database for user and prompt metadata, a distributed store for run histories and evaluation results, and a data warehouse for analytics. Emphasize scalability, consistency, and cost-efficiency, and discuss trade-offs between SQL and NoSQL, sharding, and caching.

Pro tip: Show awareness of multi-tenancy and data isolation, especially for per-user data, and mention how you'd handle GDPR/CCPA compliance and data retention policies. Also, highlight the importance of observability and monitoring in a large-scale system.

1. Clarify Requirements and Scale

Ask about expected data volume, read/write patterns, latency requirements, and consistency needs. Understand the types of data: prompts (text), run histories (time-series), evaluation results (structured), and per-user data (relational).

2. Propose High-Level Architecture

Outline a polyglot persistence approach: use a relational DB (e.g., PostgreSQL) for user data and prompt metadata, a wide-column store (e.g., Cassandra) or time-series DB for run histories, and a document store or data warehouse for evaluation results. Consider a message queue for asynchronous processing.

3. Detail Data Modeling and Partitioning

Explain how to model each entity: e.g., prompts with versioning, run histories with time-based partitioning, evaluation results with denormalization for query efficiency. Discuss sharding strategies (e.g., by user_id or time) and indexing.

4. Address Scalability and Performance

Discuss horizontal scaling, replication, caching (e.g., Redis for hot data), and read replicas. Mention trade-offs between consistency and availability (CAP theorem) and how to handle large writes (e.g., batch inserts).

5. Cover Security, Compliance, and Operations

Talk about encryption at rest and in transit, access controls, and data isolation per user. Mention backup, disaster recovery, and monitoring. Highlight compliance with regulations like GDPR.

Key Points to Mention

  • Polyglot persistence: choosing the right database for each data type (relational, NoSQL, time-series).
  • Sharding and partitioning strategies to scale horizontally, e.g., by user_id or time.
  • Caching layers (e.g., Redis) to reduce latency for frequently accessed data like prompts.
  • Asynchronous processing with message queues (e.g., Kafka) for run histories and evaluations.
  • Data isolation and multi-tenancy for per-user data, ensuring security and compliance.
  • Trade-offs between consistency, availability, and partition tolerance (CAP theorem) in distributed systems.

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