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

SeniorPrefer not to say
Apr 2026Remote

Summary

System design round at Abridge for a software engineering role, focused entirely on redesigning a medical audio pipeline. The scope was pretty wide, covering security, compliance, and performance all at once, which made it feel less like a single question and more like a 45-minute architecture conversation.

Questions Asked (5)

Q1

You have a medical audio pipeline: audio in, speech-to-text, LLM summary, then persistent storage. Redesign it to be both secure and compliant with healthcare data requirements, and also make it performant at scale.

System DesignTechnical Trade-offsAPI & Integrations
Author's notes

This one is deceptively wide.

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AI HintsAI Generated

Suggested Approach

Start by clarifying requirements and constraints, then walk through the pipeline stages while addressing security, compliance, and scalability at each step. Propose a redesigned architecture that incorporates encryption, access controls, audit logging, and scalable components like message queues and auto-scaling services.

Pro tip: Demonstrate awareness of healthcare regulations like HIPAA and the importance of end-to-end encryption and audit trails; also mention trade-offs between latency and accuracy in speech-to-text and LLM summarization.

1. Clarify Requirements and Constraints

Ask about expected scale, latency requirements, compliance standards (e.g., HIPAA, GDPR), and data sensitivity. Confirm the need for auditability and data retention policies.

2. Analyze Current Pipeline and Identify Gaps

Break down the existing pipeline: audio ingestion, STT, LLM summarization, storage. Identify security, compliance, and performance bottlenecks at each stage.

3. Design Secure and Compliant Architecture

Propose encryption in transit and at rest, access controls (RBAC), audit logging, and data anonymization where possible. Ensure compliance with regulations like HIPAA by using BAAs with cloud providers.

4. Scale for Performance

Introduce asynchronous processing with message queues (e.g., Kafka, SQS), auto-scaling for STT and LLM services, caching, and CDN for audio ingestion. Consider sharding and partitioning for storage.

5. Discuss Trade-offs and Monitoring

Address trade-offs between latency, cost, and accuracy. Propose monitoring, alerting, and logging for performance and security incidents.

Key Points to Mention

  • End-to-end encryption for data in transit and at rest, including audio, transcripts, and summaries.
  • Role-based access control (RBAC) and audit logging to track data access and modifications.
  • Use of compliant cloud services (e.g., AWS HIPAA-eligible services) and Business Associate Agreements (BAAs).
  • Scalable architecture with message queues, microservices, and auto-scaling groups.
  • Data retention and deletion policies to comply with regulations.
  • Trade-offs between real-time processing and batch processing for cost and latency.

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

Q2

How would you handle access control and auditability for a pipeline processing sensitive patient data?

System DesignTechnical Trade-offs
Author's notes

Talked through role-based access and audit logs.

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AI HintsAI Generated

Suggested Approach

Start by acknowledging the regulatory context (HIPAA, GDPR) and the need for defense-in-depth. Then walk through the pipeline stages, describing how you'd enforce least-privilege access at each layer and capture immutable audit logs. Finally, discuss trade-offs between security, performance, and developer velocity.

Pro tip: Emphasize that auditability isn't just logging—it's about tamper-evident, queryable records that support both compliance and incident response. Mention that you'd design access controls to be declarative and version-controlled, so they're testable and reviewable like code.

1. Identify data flows and trust boundaries

Map where sensitive data enters, is processed, stored, and exits the pipeline. Identify trust boundaries between services, users, and external systems to determine where access controls must be enforced.

2. Define access control model

Choose an appropriate model (RBAC, ABAC, or ReBAC) based on granularity needs. Enforce least privilege at every layer: network, service, data, and user. Use short-lived credentials and just-in-time access where possible.

3. Implement audit logging and monitoring

Log all access and data operations with sufficient context (who, what, when, where, why). Ensure logs are immutable, centralized, and protected. Set up real-time alerts for anomalous access patterns.

4. Address data protection and privacy

Apply encryption at rest and in transit, tokenization or pseudonymization where feasible, and data minimization. Ensure that audit logs themselves don't leak sensitive data.

5. Discuss trade-offs and operational concerns

Balance security with performance, cost, and developer experience. Consider how to test access controls, handle key rotation, and manage compliance reporting. Mention the importance of regular audits and penetration testing.

Key Points to Mention

  • Regulatory compliance: HIPAA, GDPR, and other relevant standards for patient data.
  • Least privilege and zero-trust principles applied throughout the pipeline.
  • Immutable, tamper-evident audit logs with centralized storage and retention policies.
  • Encryption and tokenization for data at rest and in transit.
  • Role-based or attribute-based access control (RBAC/ABAC) with fine-grained policies.
  • Trade-offs: performance overhead, complexity, and impact on developer workflows.

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

Q3

How do you defend against prompt injection in an LLM pipeline that processes medical transcripts?

System DesignTechnical Trade-offs
Author's notes

Blanked for a second here.

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AI HintsAI Generated

Suggested Approach

Start by framing the problem as a security and reliability challenge specific to medical transcripts, where errors can have clinical consequences. Then walk through a defense-in-depth strategy that combines input sanitization, architectural isolation, and output validation, while acknowledging trade-offs between security and latency/accuracy. Emphasize the need for continuous monitoring and adaptation as attack vectors evolve.

Pro tip: Mention that in healthcare, prompt injection isn't just a security risk—it's a patient safety issue, so defenses must be auditable and fail-safe. Also, highlight that you'd collaborate with clinical experts to define acceptable outputs and edge cases.

1. Understand the Threat Model

Identify potential injection points in the pipeline (e.g., user input, third-party APIs, transcript metadata) and the possible impacts (e.g., data leakage, incorrect summaries, harmful recommendations). Consider both malicious attacks and accidental injections from noisy data.

2. Implement Input Sanitization and Validation

Preprocess transcripts to remove or neutralize suspicious patterns (e.g., instruction-like phrases, unusual formatting). Use allowlists for expected content and validate against medical terminology to flag anomalies.

3. Isolate and Constrain the LLM

Run the LLM in a sandboxed environment with limited permissions. Use system prompts that explicitly forbid executing instructions from user input and enforce strict output formats (e.g., JSON schema) to prevent unintended actions.

4. Validate and Sanitize Outputs

Post-process LLM outputs to detect and filter out malicious or nonsensical content. Cross-check with medical knowledge bases and apply rule-based checks for consistency and safety.

5. Monitor and Iterate

Log all inputs and outputs for auditing, set up alerts for suspicious activity, and regularly update defenses based on new attack patterns. Conduct red-team exercises to test resilience.

Key Points to Mention

  • Defense-in-depth: multiple layers of security rather than relying on a single solution.
  • Use of structured prompts and output schemas to constrain LLM behavior.
  • Importance of context-aware filtering that understands medical terminology.
  • Trade-offs between security measures and system latency/accuracy.
  • Need for human-in-the-loop review for high-risk outputs.
  • Compliance with healthcare regulations (e.g., HIPAA) and auditability.

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

Q4

Walk me through how you'd make this pipeline reliable, specifically around retries and handling failures.

System DesignAPI & Integrations
Author's notes

Idempotency keys and dead-letter queues.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the pipeline's purpose, data volume, and failure modes. Then outline a layered reliability strategy: idempotent processing, retries with backoff, dead-letter queues, and monitoring. Emphasize trade-offs and how you'd validate the approach.

Pro tip: Show you understand that retries alone can cause duplicate processing or amplify failures; always pair retries with idempotency and circuit breakers. Also, mention that you'd start with simple solutions and iterate based on observed failure patterns.

1. Clarify requirements and failure modes

Ask about data volume, latency SLAs, and what constitutes a failure (e.g., transient errors, data corruption, downstream outages). Identify critical paths and potential bottlenecks.

2. Design for idempotency and exactly-once semantics

Ensure each step can be safely retried without side effects. Use unique keys, deduplication, or transactional writes to achieve exactly-once processing where needed.

3. Implement retry policies with backoff and jitter

Configure retries for transient failures with exponential backoff and jitter to avoid thundering herd. Set maximum retry limits and timeouts to prevent infinite loops.

4. Add dead-letter queues and alerting

Route persistently failing messages to a dead-letter queue for manual inspection. Set up alerts on queue depth, error rates, and latency to detect issues early.

5. Monitor, test, and iterate

Instrument the pipeline with metrics and tracing. Conduct chaos testing to validate failure handling. Continuously refine based on production incidents and feedback.

Key Points to Mention

  • Idempotency: using unique identifiers or idempotent operations to avoid duplicate processing on retry.
  • Exponential backoff with jitter: reducing load on failing services and avoiding synchronized retries.
  • Dead-letter queues: capturing and isolating messages that repeatedly fail for later analysis.
  • Circuit breakers: preventing cascading failures by temporarily halting requests to a failing service.
  • Monitoring and alerting: tracking error rates, retry counts, and queue depths to ensure visibility.
  • Trade-offs: balancing reliability with latency and cost, and choosing between at-least-once vs exactly-once semantics.

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

Q5

What performance optimizations would you apply to the transcription and LLM summarization steps to reduce latency and cost at scale?

System DesignTechnical Trade-offs
Author's notes

Chunked streaming transcription, async fan-out, batching LLM calls, caching repeated content, autoscaling on queue depth.

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AI HintsAI Generated

Suggested Approach

Structure your answer by first breaking down the pipeline into transcription and summarization stages, then for each stage discuss latency and cost optimizations separately. Emphasize trade-offs between accuracy, latency, and cost, and propose a balanced solution that scales. Use concrete techniques like streaming, batching, caching, and model selection.

Pro tip: Mention that you would instrument the pipeline to measure latency and cost per stage, then optimize the bottleneck first—often transcription is the latency bottleneck while summarization is the cost bottleneck. This shows a data-driven approach.

1. Analyze the pipeline and identify bottlenecks

Break down the transcription and summarization steps, measure latency and cost for each, and identify where the biggest gains can be made. Consider factors like audio length, model size, and request patterns.

2. Optimize transcription for latency and cost

Use streaming transcription to reduce perceived latency, choose efficient models (e.g., distilled versions), and leverage batching or asynchronous processing. Consider caching frequent phrases or using on-device processing where possible.

3. Optimize LLM summarization for latency and cost

Employ techniques like prompt compression, few-shot examples to reduce output length, and model distillation. Use caching for similar summaries, batch requests, and consider smaller models for simpler cases with fallback to larger models when needed.

4. Implement caching and reuse

Cache transcription results for repeated audio and summaries for similar transcripts. Use semantic caching to reuse summaries for semantically similar inputs, reducing redundant LLM calls.

5. Monitor and iterate with trade-offs

Continuously monitor latency and cost metrics, and adjust based on trade-offs between accuracy and efficiency. Use A/B testing to validate optimizations and ensure quality is maintained.

Key Points to Mention

  • Streaming transcription to reduce latency
  • Model selection: smaller/distilled models for cost and speed
  • Batching and asynchronous processing for throughput
  • Caching strategies (exact match and semantic) to avoid redundant work
  • Prompt engineering and compression to reduce LLM token usage
  • Trade-offs between accuracy, latency, and cost; measure and optimize bottlenecks

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