How SQL query optimization builds your execution plan
9 min read A walkthrough of sql query optimization for interviews: how the planner turns your query into a cost-based execution plan, and where those plans go wrong. Read article
System Design
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// system-design
System Design
Distributed systems, scalability, and architecture — from URL shorteners to Netflix-scale streaming, with the tradeoffs interviewers probe.
System Design
Kafka interview questions that separate users from operators
9 min read A walkthrough of the Kafka questions interviewers actually ask, covering partitions, consumer groups, rebalancing, and delivery guarantees. Read article
System Design
The limit order book question every trading interview reaches
8 min read How trading firms grade the in-memory order book design problem, from the data structures that keep cancels O(1) to the follow-ups on price-time priority and self-trade prevention. Read article
System Design
The post-quantum crypto questions security interviews now ask
6 min read How security and platform interviews probe ML-KEM, hybrid key exchange, and moving real systems off RSA before quantum computers arrive. Read article
System Design
Inside the FPGA interview at a low-latency trading firm
7 min read What a low-latency trading desk actually probes when it interviews FPGA and hardware engineers. Read article
System Design
Why HFT desks won’t let the kernel touch a market-data packet
7 min read How high-frequency trading firms map the network card straight into user space, which tools do it, and what interviewers grade when they ask about the packet path. Read article
System Design
Why adding a cache node shouldn’t move every key
7 min read The math behind hash rings, why virtual nodes exist, and what a designer probes the moment you reach for consistent hashing. Read article
System Design
What Kubernetes interviewers actually ask once you’re past pods
8 min read The pod and service definitions get you through the phone screen; the failure scenarios decide the onsite. Read article
System Design
How the TLS handshake works, and what interviewers probe
7 min read A walkthrough of the TLS 1.3 handshake, forward secrecy, certificate validation, 0-RTT replay risk, and the post-quantum key exchange interviewers started asking about in 2026. Read article
System Design
Why interviewers keep asking if you can revoke a JWT
7 min read A senior-level walk through the OAuth, OIDC, and JWT questions that come up in backend and security interviews, and the answers that actually land. Read article
System Design
Designing a matching engine that keeps price-time priority
7 min read How exchanges match buy and sell orders, why the hot path runs on a single thread, and how the book rebuilds itself after a crash. Read article
System Design
When to partition, when to shard, and when to just replicate
7 min read The difference between partitioning, sharding, and replication that interviewers keep probing, and how to reason about which one a system actually needs. Read article
System Design
How NoSQL data modeling questions test query-first thinking
6 min read A walkthrough of the DynamoDB, Cassandra, and MongoDB modeling questions that show up in system design rounds, and how to reason through them. Read article
System Design
What happens after you hit enter, and why interviewers ask
7 min read A layer-by-layer walk through what happens between hitting enter and a page loading, and the follow-ups interviewers push on at each step. Read article
System Design
HTTP methods and status codes that trip up backend interviews
7 min read A working reference for HTTP methods and status codes, with the safe-versus-idempotent distinction and the codes interviewers keep probing. Read article
