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

SeniorPrefer not to say

May 2026Remote

Summary

System design round at HubSpot for a software engineering role. The prompt was basically 'build Netflix' which sounds exciting until you realize how many moving parts they actually want you to cover in 45 minutes.

Questions Asked (1)

Design a large-scale video streaming platform similar to Netflix. Walk through the full system including user auth, content catalog, search, recommendations, video processing, DRM, adaptive streaming, CDN strategy, storage, playback sessions, APIs, multi-region failover, observability, and cost optimization for millions of concurrent users.

System DesignTechnical Trade-offsA/B Testing & Experimentation

Author's notes

This is one of those questions where the scope is so wide you could spend three hours on it and still feel like you skimmed everything.

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AI HintsAI Generated

Suggested Approach

Start by clarifying requirements and scale (e.g., millions of concurrent users, global reach), then outline the high-level architecture before diving into each component. Focus on key trade-offs (e.g., consistency vs. availability, cost vs. performance) and how they impact the design. Conclude by discussing observability and cost optimization to show end-to-end thinking.

Pro tip: Emphasize that at HubSpot's scale, you'd leverage existing cloud services (e.g., AWS MediaConvert, CloudFront) rather than building everything from scratch, and highlight how you'd measure success through A/B testing and metrics.

1. Clarify Requirements and Scope

Ask questions to understand expected scale (users, concurrent streams, regions), content types (movies, series), and non-functional requirements (latency, availability, DRM). This ensures you design for the right constraints.

2. High-Level Architecture

Sketch the major components: client apps, API gateway, auth service, content catalog, search, recommendations, video processing pipeline, DRM, CDN, storage, playback sessions, and observability. Explain how they interact.

3. Deep Dive into Critical Components

Pick 2-3 areas to detail, such as video processing (transcoding, packaging), adaptive streaming (HLS/DASH), CDN strategy (multi-CDN, edge caching), and multi-region failover. Discuss trade-offs and technologies.

4. Address Scalability, Reliability, and Cost

Explain how the system scales to millions of concurrent users (e.g., horizontal scaling, sharding, caching), ensures high availability (redundancy, failover), and optimizes cost (storage tiers, CDN pricing, spot instances).

5. Wrap Up with Observability and Experimentation

Describe monitoring, logging, and tracing for observability, and how you'd use A/B testing to improve recommendations and user experience. Summarize key decisions and trade-offs.

Key Points to Mention

Adaptive streaming using HLS/DASH with multiple bitrate ladders for varying network conditions.
Multi-CDN strategy with dynamic routing to optimize performance and cost.
DRM integration (e.g., Widevine, FairPlay) for content protection.
Recommendation system using collaborative filtering and real-time personalization.
Multi-region active-active deployment with data replication and failover mechanisms.
Cost optimization via storage lifecycle policies, CDN caching, and reserved instances.

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