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

Senior
May 2026

Summary

Palantir system design round for a software engineer role. The whole thing was one big open-ended design question about an internal employee interest-matching platform, and they pushed hard on every layer of the stack.

Questions Asked (5)

Q1

Design a system that connects employees across a company based on shared interests. Walk through the key features, data model, storage choices, APIs, matching logic, and how you'd handle privacy and access control for an internal-only tool.

System DesignData ModelingTechnical Trade-offs
Author's notes

This felt like five questions crammed into one.

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AI HintsAI Generated

Suggested Approach

Start by clarifying requirements and constraints (internal-only, privacy, scale) before diving into design. Then walk through the system layer by layer: data model, storage, APIs, matching, and access control, emphasizing trade-offs and privacy-by-design. Conclude by discussing how you'd iterate and measure success.

Pro tip: Emphasize privacy and access control from the start—treat them as first-class design constraints, not afterthoughts. Show awareness that in an internal tool, trust and adoption depend on employees feeling safe sharing interests.

1. Clarify Requirements and Constraints

Ask questions to understand scale (number of employees), privacy expectations, and integration with existing systems (e.g., HR, SSO). Define what 'shared interests' means and how they are captured.

2. Design Data Model and Storage

Propose entities: Employee, Interest, EmployeeInterest, and possibly Group. Choose storage: relational DB for structured data, graph DB for relationships, or a hybrid. Discuss indexing for efficient lookups.

3. Define APIs and Matching Logic

Outline REST or GraphQL APIs for CRUD on interests and for querying matches. Describe matching algorithms: exact match, weighted similarity, or collaborative filtering. Consider batch vs. real-time.

4. Implement Privacy and Access Control

Detail authentication (SSO), authorization (RBAC/ABAC), and privacy controls (opt-in, visibility settings). Ensure data minimization and audit logging. Discuss how to prevent unauthorized access or inference.

5. Discuss Trade-offs and Scalability

Compare storage options, matching complexity, and privacy vs. utility. Address scaling: sharding, caching, and asynchronous processing. Mention monitoring and iteration.

Key Points to Mention

  • Privacy-by-design: opt-in interests, granular visibility controls, and anonymization where possible.
  • Access control: integrate with company SSO, enforce RBAC, and log access for audits.
  • Data model: many-to-many relationship between employees and interests; consider graph DB for efficient traversal.
  • Matching logic: start with simple exact match, then evolve to weighted or ML-based similarity.
  • API design: RESTful endpoints for interests and matches, with pagination and filtering.
  • Scalability: use caching, asynchronous matching, and sharding for large employee bases.

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

Q2

How would you approach the cold start problem for new employees who haven't set up a profile or tagged any interests yet?

System DesignProduct Sense & Ideation
Author's notes

Blanked for a second here.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the product context and constraints, then propose a multi-pronged strategy that combines explicit onboarding signals, implicit behavioral data, and smart defaults. Emphasize iterative improvement through feedback loops and measurable success metrics, while addressing privacy and fairness concerns.

Pro tip: Frame the cold start problem as an opportunity to design a progressive profiling system that learns from user actions, rather than requiring upfront data. Show awareness of Palantir's emphasis on data-driven solutions and ethical considerations.

1. Clarify the problem and constraints

Ask questions to understand the product, user base, and what 'cold start' means in this context (e.g., no profile, no tags, no interactions). Identify available data sources and business goals.

2. Leverage explicit and implicit signals

Propose using onboarding flows to collect minimal explicit preferences, while also capturing implicit signals from user behavior (e.g., clicks, time spent) to infer interests.

3. Apply smart defaults and content-based methods

Suggest using demographic or role-based defaults, popular items, or content-based filtering to provide initial recommendations until enough data is gathered.

4. Design for iterative learning and feedback

Outline a system that continuously updates user profiles based on interactions, using collaborative filtering and online learning to improve recommendations over time.

5. Define success metrics and address risks

Specify metrics like engagement, retention, and satisfaction to evaluate the approach. Discuss potential biases, privacy concerns, and mitigation strategies.

Key Points to Mention

  • Hybrid approach: combine content-based filtering, collaborative filtering, and demographic defaults.
  • Progressive profiling: start with minimal data and enrich over time through user interactions.
  • Use of implicit feedback (e.g., clicks, dwell time) to infer interests without explicit tags.
  • Cold start as a classification or exploration-exploitation problem (e.g., multi-armed bandits).
  • Privacy and ethical considerations: ensure transparency and user control over data.
  • Evaluation metrics: measure improvement in engagement and retention, and iterate based on A/B tests.

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

Q3

What ranking signals would you use to surface the most relevant employee connections, and how would you update those rankings in near real-time as interests change?

System DesignProduct Analytics & MetricsTechnical Trade-offs
Author's notes

I talked through a mix of static signals like shared tags and team proximity, and dynamic ones like recent activity or newly added interests.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the product context and success metrics, then propose a multi-signal ranking model that balances offline and online signals. Describe a streaming architecture for near real-time updates, and discuss trade-offs like latency, freshness, and cold-start. Conclude with evaluation and iteration strategies.

Pro tip: Emphasize that ranking is an iterative process: start with a simple heuristic, measure, and then incorporate ML. Also, highlight the importance of explainability and user control to build trust.

1. Clarify Requirements and Metrics

Ask questions to understand the product goals, user expectations, and how success is measured (e.g., connection acceptance rate, engagement). Define what 'relevant' means in this context.

2. Identify Ranking Signals

List potential signals: profile similarity, shared projects, communication frequency, recency of interactions, mutual connections, and explicit interests. Categorize into static (slow-changing) and dynamic (fast-changing) signals.

3. Design Near Real-Time Update Architecture

Propose a streaming pipeline (e.g., Kafka, Flink) to process events like profile updates, interactions, and feedback. Use a feature store to serve fresh features to the ranking model with low latency.

4. Address Trade-offs and Challenges

Discuss trade-offs: freshness vs. computational cost, personalization vs. privacy, and cold-start for new employees. Suggest techniques like incremental learning, caching, and fallback strategies.

5. Evaluate and Iterate

Outline an evaluation framework: offline metrics (NDCG, precision@k) and online A/B tests. Plan for continuous monitoring and model retraining to adapt to changing interests.

Key Points to Mention

  • Multi-signal ranking model combining static and dynamic features
  • Streaming architecture for near real-time updates (e.g., Kafka, Flink)
  • Feature store for low-latency feature serving
  • Trade-offs: latency, freshness, cost, privacy
  • Cold-start problem and fallback strategies
  • Evaluation metrics and online experimentation

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

Q4

Describe the high-level architecture for this system, including the services, databases, search indices, caching layer, and event/queue infrastructure.

System DesignTechnical Trade-offsAPI & Integrations
Author's notes

Went with a pretty standard microservices split: a profile service, an interest/tagging service, a recommendation engine, and a messaging service.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the system's core requirements and scale, then sketch a high-level architecture that separates concerns into services, data stores, and infrastructure. Walk through each layer (services, databases, search, caching, events) explaining the role and key trade-offs, and conclude by discussing how they interact to meet the requirements.

Pro tip: Emphasize trade-offs and justify each component choice based on the specific requirements (e.g., consistency vs. availability, latency vs. cost). Palantir values pragmatic, scalable designs that handle real-world constraints.

1. Clarify Requirements and Constraints

Ask questions to understand functional and non-functional requirements: expected scale (QPS, data volume), latency, consistency, availability, and budget. This ensures your design is tailored to the problem.

2. Outline Core Services

Identify the main services (e.g., API gateway, authentication, business logic, data processing) and their responsibilities. Explain how they communicate (sync/async) and how they scale independently.

3. Design Data Storage Layer

Choose appropriate databases (SQL/NoSQL) for different needs, and describe search indices (e.g., Elasticsearch) and caching layers (e.g., Redis) with their roles. Discuss data models, replication, and sharding.

4. Incorporate Event/Queue Infrastructure

Explain how events and queues (e.g., Kafka, RabbitMQ) enable decoupling, async processing, and reliability. Describe key event flows and how they integrate with services and data stores.

5. Summarize and Discuss Trade-offs

Recap the architecture, highlighting how components interact to meet requirements. Discuss trade-offs made (e.g., CAP theorem, cost vs. performance) and potential bottlenecks or failure modes.

Key Points to Mention

  • Separation of concerns and microservices vs. monolith trade-offs
  • Database choices: SQL vs. NoSQL, replication, sharding, and consistency models
  • Search indices (e.g., Elasticsearch) for full-text search and analytics
  • Caching strategies (e.g., Redis, CDN) for latency reduction and load shedding
  • Event-driven architecture with queues (e.g., Kafka) for scalability and decoupling
  • Scalability, fault tolerance, and monitoring/observability considerations

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

Q5

How does this system scale to tens of thousands of employees, and what monitoring and abuse prevention would you put in place?

System DesignProduct Analytics & Metrics
Author's notes

Scaling I handled fine, horizontal scaling on stateless services, sharding the interest graph, read replicas.

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AI HintsAI Generated

Suggested Approach

Start by clarifying the system's purpose and scale requirements, then outline a scalable architecture using horizontal scaling, sharding, and caching. Address monitoring with metrics, logging, and alerting, and abuse prevention with rate limiting, anomaly detection, and audit trails. Tie everything back to Palantir's focus on security and data integrity.

Pro tip: Emphasize that scaling isn't just about infrastructure—it's about designing for observability and abuse resistance from day one. Mention specific tools like Prometheus for metrics and Kafka for event streaming to show practical knowledge.

1. Clarify Requirements and Assumptions

Ask about the system's current architecture, expected growth, and specific abuse concerns. State assumptions about read/write ratios, data volume, and latency requirements.

2. Design for Horizontal Scalability

Propose a distributed architecture with sharding, replication, and load balancing. Discuss partitioning strategies (e.g., by employee ID or geography) and caching layers to handle tens of thousands of users.

3. Implement Comprehensive Monitoring

Outline a monitoring stack: metrics (Prometheus/Grafana), logging (ELK), tracing (Jaeger), and alerting (PagerDuty). Define key SLIs/SLOs like latency, error rates, and throughput.

4. Build Abuse Prevention Mechanisms

Describe rate limiting, authentication/authorization (RBAC), anomaly detection (ML-based), and audit logging. Include data encryption and compliance checks.

5. Iterate and Validate

Suggest load testing, chaos engineering, and regular security audits. Emphasize continuous improvement based on monitoring data and feedback loops.

Key Points to Mention

  • Horizontal scaling via sharding and replication to distribute load
  • Caching strategies (Redis, CDN) to reduce database pressure
  • Monitoring with metrics, logging, and distributed tracing (e.g., Prometheus, ELK, Jaeger)
  • Rate limiting and throttling to prevent API abuse
  • Anomaly detection using machine learning for unusual access patterns
  • Audit trails and RBAC for compliance and security

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