For a book selling platform, the key decisions are search architecture (Elasticsearch vs full-text search), inventory consistency (strong vs eventual), and order state machine design.
DDIA Chapter 1's core argument: the challenge of data-intensive systems isn't big compute — it's data complexity (volume, variety, velocity). Evaluating this complexity requires precise definitions of reliability, scalability, and maintainability that are more specific than how most engineers use these terms.
The hardest part of designing Uber isn't picking the right technologies — it's breaking a vague, enormous problem into discussable sub-problems
AI Agents let models perceive environments and act autonomously. Harness Engineering is the discipline that makes them reliable — the scaffolding that turns a smart-but-unpredictable model into a deployable engineering system.
Redis is an in-memory data structure server that achieves sub-millisecond latency through a single-threaded event loop, rich data types, and all-RAM storage. It's the go-to for caching, sessions, leaderboards, rate limiting — and in 2026, AI agent memory.
Cursor is an AI-powered code editor by Anysphere, built by four MIT graduates, that hit $500M ARR within two years of launch. This article distills the real engineering lessons they've shared publicly: why they forked VSCode instead of building an extension, how Tab prediction's latency engineering works, and the hard production lessons from shipping Agent Mode.
Sora's core architecture is a Diffusion Transformer (DiT): compress video into spatiotemporal patch tokens, train a diffusion model to denoise them, with the Transformer handling global coherence. The real engineering challenges are temporal consistency, variable-length/resolution support, and training scale.
The Data Lakehouse merges the ACID reliability of data warehouses with the low-cost open storage of data lakes. Apache Iceberg and Delta Lake are the two dominant open table formats making this architecture practical at scale.
The point of system design interviews isn't memorizing answers — it's demonstrating that you can derive design decisions from first principles. Knowing Kafka, Redis, and consistent hashing cold doesn't help; explaining 'why this approach in this context, and what it costs' is what actually matters.
The DoorDash donation feature is a classic high-concurrency, eventual consistency problem: millions of users triggering small donations at checkout, with a rolling live total displayed in real time. The core trade-off is strong consistency (dual-write + 2PC) vs. eventual consistency (event-driven + counter aggregation).