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KNOWLEDGE LIBRARY

Playbooks, system concepts, case studies, and insights for Technical Business Analysts and Product Managers.

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playbooks-cracking-product-discovery-questions
PlaybookApr 11, 2026

How to Crack Product Discovery Questions in PM Interviews

Product discovery questions don't test what you know — they test how you find the right problem. This article breaks down the common question types, the core thinking framework, and real examples so you can answer with confidence from round one.

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case-studies-slack-presence-state-architecture-tradeoffs
Case StudyApr 11, 2026

Slack's "Green Dot" Problem: The Nightmare of Real-Time Architecture

Displaying an online status seems basic, but it becomes an infrastructure nightmare at scale. Discover how Slack restructured its Pub/Sub model to balance real-time accuracy with server costs.

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insights-failed-anthropic-interview-ai-prep-trap
InsightApr 10, 2026

System Design: The AI Over-Engineering Trap

AI models are trained on Big Tech engineering blogs, leading them to suggest Kubernetes and Kafka for everything. Learn why this bias causes candidates to fail System Design interviews and how to ground your architecture in actual throughput math.

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system-concepts-preventing-oversell-atomic-operations
System ConceptApr 10, 2026

Preventing Oversell: Atomic Operations & Locking

Explore the trade-offs between Pessimistic Locking, Redis Transactions, and Lua Scripts in preventing inventory overselling during high-concurrency events.

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playbooks-master-whiteboard-design-challenge-pm
PlaybookApr 08, 2026

5 Steps to Master the PM Whiteboard Design Challenge

The whiteboard interview isn't an art test; it's an evaluation of systems thinking and ambiguity management. Master this 5-step framework to structure your problem-solving and demonstrate razor-sharp Product Sense.

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system-concepts-virtual-waiting-room
System ConceptApr 08, 2026

Virtual Waiting Room: When "Virtual Queues" Save Both the System and the User Experience

Blocking 90% of traffic might sound effective—but to users, it’s just a 503 error and the feeling of a system crash. A Virtual Waiting Room solves the same technical challenge but wraps it in a controlled experience: users know exactly where they stand in line, while the backend remains fully protected.

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system-concepts-tai-sao-khong-luu-hinh-anh-trong-postgres
System ConceptApr 06, 2026

Why You Shouldn't Store Images in a Database

Storing large binary data in a relational database destroys buffer pool efficiency and inflates operational costs. Discover how Postgres manages data via 8KB pages and why Blob Storage is mandatory for scale.

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playbooks-product-requirements-document-core-mindset
PlaybookApr 05, 2026

Stop Memorizing Templates: The Core PRD Mindset

Lost in a sea of different PRD/SRS formats? Instead of memorizing templates, master the core analytical mindset and the 4 immutable pillars every product document must have.

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Thiết kế Hệ thống Flash Sale: Hiển thị Tồn kho Real-time Không Làm Sập Database
System ConceptApr 04, 2026

Flash Sale System Design: Achieving "Real-Time" Inventory Without Crashing the Database

When millions of users rush to buy a single item, querying the database directly is a death sentence for your system. This article decodes the Cache-First and Message Queue architecture that maintains inventory accuracy while ensuring high availability.

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