#Geospatial

System DesignSep 12, 2026

Design Uber — Geospatial Matching, Live Location, and Surge Pricing

A system design walkthrough of Uber: geospatial indexing (geohash/quadtree/H3), finding nearby drivers, rider matching, live location, and surge pricing.

13 min read9

System Design

System DesignSep 11, 2026

Design a Payment System — Idempotency, Ledgers, and Exactly-Once at Scale

A system design walkthrough of a payment system: idempotency, the double-entry ledger, exactly-once processing, and reconciliation with the provider.

14 min read8

System Design

System DesignSep 9, 2026

Design WhatsApp — Real-Time Messaging, Delivery Receipts, and Presence at Scale

A system design walkthrough of WhatsApp: WebSocket delivery, message ordering, delivery and read receipts, online presence, and group fan-out at scale.

14 min read11

System Design

System DesignSep 8, 2026

Design a News Feed (Twitter/Facebook) — Fan-out, Ranking, and the Celebrity Problem

A system design walkthrough of a news feed like Twitter or Facebook: fan-out on write vs read, the celebrity problem, ranking, and caching at scale.

14 min read3

System Design

System DesignSep 5, 2026

Design a Notification System — Push, SMS & Email at Scale

A system design walkthrough of a notification system: multi-channel fan-out (push, SMS, email), queues, retries, dedup, and delivery at scale.

14 min read9

System Design

System DesignSep 4, 2026

Design a Distributed Cache — Consistent Hashing, Eviction, and Replication

A system design walkthrough of a distributed cache like Redis/Memcached: consistent hashing, eviction policies, replication, and write strategies.

14 min read9

System Design

System DesignSep 2, 2026

Design a Rate Limiter — Token Bucket, Sliding Window, and Distributed Limits

A system design walkthrough of a rate limiter: token bucket vs sliding window, where it lives, and making limits work across a distributed fleet.

14 min read24

System Design

System DesignSep 1, 2026

Design a URL Shortener (bit.ly) — The Complete System Design Walkthrough

A full system design walkthrough for a URL shortener like bit.ly: requirements, estimates, short-code generation, caching, and scaling to billions.

18 min read14

System Design

System DesignAug 30, 2026

How to Crack Any System Design Interview: A Repeatable Framework

Most people fail system design interviews for lack of a method, not knowledge. Here's a repeatable framework to design any system in 45 minutes.

15 min read22

React

ReactAug 29, 2026

Authentication and Authorization in React — JWT, Refresh Tokens, RBAC, Azure AD, OAuth2 (Real Code, Production Patterns)

Production-grade React auth: short-lived JWT in memory, rotating refresh tokens, server-enforced RBAC, Azure AD via MSAL, OAuth2 + PKCE — real code.

30 min read18

System Design

System DesignAug 27, 2026

Event-Driven Architecture in .NET — Why, How, Real Code (ASP.NET Core + React), Production Tuning, and When NOT to Use It

Event-driven architecture in .NET: why choose it, problems solved, challenges, a full diagram, real ASP.NET Core + React code, and when NOT to use it.

34 min read16

React

ReactAug 26, 2026

React and AI — Building a ChatGPT-Like Application with Streaming, OpenAI APIs, RAG, and Vector Databases (Real Code, Production Metrics)

Stream tokens, ground answers in your docs with RAG, and use pgvector — the production playbook for a ChatGPT-style app in React with real metrics.

22 min read12

Posts

Design Uber — Geospatial Matching, Live Location, and Surge Pricing

Design a Payment System — Idempotency, Ledgers, and Exactly-Once at Scale

Design WhatsApp — Real-Time Messaging, Delivery Receipts, and Presence at Scale

Design a News Feed (Twitter/Facebook) — Fan-out, Ranking, and the Celebrity Problem

Design a Notification System — Push, SMS & Email at Scale

Design a Distributed Cache — Consistent Hashing, Eviction, and Replication

Design a Rate Limiter — Token Bucket, Sliding Window, and Distributed Limits

Design a URL Shortener (bit.ly) — The Complete System Design Walkthrough

How to Crack Any System Design Interview: A Repeatable Framework

Authentication and Authorization in React — JWT, Refresh Tokens, RBAC, Azure AD, OAuth2 (Real Code, Production Patterns)

Event-Driven Architecture in .NET — Why, How, Real Code (ASP.NET Core + React), Production Tuning, and When NOT to Use It

React and AI — Building a ChatGPT-Like Application with Streaming, OpenAI APIs, RAG, and Vector Databases (Real Code, Production Metrics)

Interview questions

When should you use a service mesh (Istio / Linkerd) instead of plain Kubernetes service discovery?

What is the difference between client-side and server-side service discovery?

How does service discovery work in Kubernetes without installing Consul or Eureka?

What is the difference between liveness and readiness probes, and why does it matter for service discovery?

What is service discovery and why do microservices need it?

Why does Python dominate AI/ML development — what are the real reasons?

Tokens, context windows, and the O(n²) attention cost — what every dev should know

LLM sampling parameters — temperature, top-p, top-k — when to tune each

What is a Large Language Model (LLM) and how does it work internally?

Open-source vs proprietary LLMs — when to pick which (Llama, Mistral, GPT, Claude)

RAG vs fine-tuning — when do you choose which?

How do you chunk documents effectively for RAG?

How do you prevent hallucinations and improve answer quality in RAG?

RAG in production — security, cost, freshness, and the patterns that matter

What is RAG (Retrieval-Augmented Generation) and what problems does it solve?