Fundamentals
System Design › FundamentalsLatency Numbers Every Engineer Should Know (with Intuition)
The famous latency numbers — cache, RAM, SSD, disk, and network round trips — explained by orders of magnitude, with a vivid mental model and how each one drives real system design decisions.
System Design › FundamentalsResilience: Timeouts, Retries & Circuit Breakers Explained
How to keep a distributed system standing when one service fails. Timeouts, retries with backoff and jitter, the circuit breaker (closed/open/half-open), plus fallbacks and bulkheads — stopping cascading failures.
System Design › FundamentalsObject Storage & Blobs (S3): Where Files Really Live
Where do the world's images, videos, and backups live? Object storage like S3 — buckets, keys, durability, object vs file vs block storage, and the golden rule: store the URL, not the blob.
System Design › FundamentalsBloom Filters Explained: The Space-Saving Magic Trick
A tiny structure that tells you an item is definitely not in a set using barely any memory. Bloom filters explained — bit arrays, hash functions, false positives, and why Cassandra and caches use them.
System Design › FundamentalsWebSockets vs Long Polling vs SSE: Real-Time on the Web
How does a server push live updates to the browser? The four real-time techniques — short polling, long polling, Server-Sent Events, and WebSockets — explained, with exactly when to pick each.
System Design › FundamentalsACID & Database Isolation Levels Explained (with Anomalies)
ACID made simple — Atomicity, Consistency, Isolation, Durability — plus the four isolation levels, the anomalies they prevent (dirty, non-repeatable, phantom reads), and how MVCC softens the trade-off.
System Design › FundamentalsReverse Proxy vs Load Balancer: What's the Difference?
A load balancer is a kind of reverse proxy — here's exactly how they relate. Forward vs reverse proxy, what each does (TLS, caching, routing, health checks), and L4 vs L7. Fresher to senior.
System Design › FundamentalsCDN Explained: How Content Delivery Networks Make Sites Fast
What a CDN is and why nearly every large site uses one — edge servers, cache hit vs miss, TTL, offloading the origin, and cache invalidation with versioned URLs. A fresher-to-senior guide.
System Design › FundamentalsMicroservices Architecture: Benefits, Costs & When Not To
What microservices actually are, why teams adopt them, the real costs of a distributed system, and — the part interviewers love — when NOT to use them. Monolith vs microservices, from fresher to senior.