Why the database ignores your index, and other indexing traps
7 min read How query planners actually decide whether to use an index, and the indexing questions that separate strong engineers in interviews. Read article
System Design
System Design
What isolation levels really guarantee, and where they leak
6 min read The four ANSI isolation levels, what each one actually prevents, and the concurrency bugs that survive even at repeatable read. Read article
System Design
Designing a vector database that stays fast at a billion vectors
7 min read A walkthrough of the real design decisions behind approximate nearest neighbor search, from choosing HNSW or IVF to sharding and filtering at scale. Read article
System Design
What interviewers actually grade in a RAG design round
6 min read What separates a passing RAG design answer from a hand-wavy one, stage by stage. Read article
Interview Prep
How Cognition hires the engineers behind Devin
6 min read Cognition’s engineering loop, the agent-infrastructure problems they put in front of you, and how to prepare for a team building autonomous coding agents. Read article
Interview Prep
How Stripe’s bug bash and API rounds decide the offer
7 min read A round-by-round look at the Stripe engineering loop, where integration, debugging, and API design weigh more than algorithm puzzles. Read article
System Design
30 System Design Building Blocks You Can Sketch From Memory
7 min read A reference grid of the thirty components that turn up in nearly every system design interview, what each one does, and where it breaks. Read article
Interview Prep
What Decagon’s engineering interview loop really tests
7 min read A walkthrough of Decagon’s engineering loop, from the agent-flavored coding round to the system design and eval questions that decide it. Read article
Tools & Reviews
Which System Design Course Actually Makes You Better
6 min read A working engineer’s take on ByteByteGo, Grokking, Hello Interview, and DesignGurus, and which one helps depending on how you tend to fail. Read article
Coding Interview Questions
How NVIDIA Tests CUDA and GPU Skills in Its Interviews
7 min read A walk through the CUDA performance questions, GPU parallelism design problems, and C++ rounds that show up in NVIDIA’s technical loop. Read article
Interview Prep
What Modal Labs actually asks backend and infra engineers
7 min read A round-by-round look at Modal Labs’ interview for backend and infrastructure roles, and the kinds of questions they actually ask. Read article
Interview Prep
How Together AI Interviews Backend and Infra Engineers
7 min read A walk through Together AI’s engineering loop, from the coding rounds to GPU-serving system design and the CUDA-flavored take-homes. Read article
System Design
Design a Recommendation Engine (Netflix-style)
5 min read Design a recommendation engine like Netflix’s, Spotify’s Discover Weekly, or Amazon’s “Customers also bought.” Recommendation systems are one of the Read article
System Design
Design an LLM Inference API
6 min read Design an LLM inference API — the service that accepts user prompts and returns model completions, like the OpenAI API, Read article
System Design
Design a Monitoring and Alerting System
6 min read Design a monitoring and alerting system like Datadog, Prometheus + Grafana, or New Relic. This is a system design problem Read article
