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

SeniorPrefer not to say
May 2026

Summary

System design round at Hebbia for a software engineer role, focused entirely on building the backend for an LLM-powered chat product in a fintech context. Pretty meaty scope: streaming responses, multi-agent orchestration, tool calls, compliance concerns, the works. Left feeling like I covered the broad strokes but probably underdeveloped the failure handling section.

Questions Asked (1)

Q1

Design the backend for an LLM-powered chat product used in a financial-technology setting. Cover the architecture, main services, data model, request flow, scaling strategy, and failure handling. The frontend is a simple chat UI but your scope is the backend only.

System DesignTechnical Trade-offsAPI & Integrations
Author's notes

This is a big one.

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AI HintsAI Generated

Suggested Approach

Start by clarifying requirements and constraints (e.g., latency, compliance, scale) and then walk through a high-level architecture before diving into each component. Focus on trade-offs, especially around LLM integration, data privacy, and scalability, and tie your decisions back to the fintech context.

Pro tip: Emphasize how you would handle sensitive financial data with LLMs, such as using on-prem or VPC-hosted models, data anonymization, and audit logging. Showing awareness of regulatory requirements (e.g., SOC2, GDPR) will set you apart.

1. Clarify Requirements and Constraints

Ask about expected scale (users, QPS), latency SLAs, compliance needs (e.g., data residency, encryption), and LLM provider options (open-source vs. API). This ensures your design meets the actual needs.

2. High-Level Architecture

Sketch the main components: API gateway, chat service, LLM orchestration, data storage, and monitoring. Explain how they interact and the flow of a request from the frontend to the LLM and back.

3. Data Model and Storage

Define schemas for conversations, messages, users, and audit logs. Discuss choices like SQL vs. NoSQL, vector databases for embeddings, and encryption at rest/in transit.

4. Scaling and Reliability

Describe how to scale each service (horizontal scaling, caching, async processing) and handle failures (retries, circuit breakers, fallback models). Mention rate limiting and load shedding.

5. Security and Compliance

Cover authentication, authorization, data anonymization, audit trails, and compliance with financial regulations. Explain how you protect sensitive data when using third-party LLMs.

Key Points to Mention

  • LLM integration patterns: synchronous vs. asynchronous, streaming responses, and fallback strategies
  • Data privacy: encryption, anonymization, and compliance (e.g., SOC2, GDPR, PCI-DSS)
  • Scalability: horizontal scaling, caching, message queues, and rate limiting
  • Failure handling: retries, circuit breakers, graceful degradation, and monitoring
  • Trade-offs: latency vs. cost, open-source vs. proprietary LLMs, consistency vs. availability
  • Observability: logging, metrics, tracing, and alerting for LLM-specific issues (e.g., hallucinations, token usage)

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