Hey, I'm Ridwan. I build Backends and Write about Tech.

A ride-hailing platform modeled on Uber: riders request trips, a matching service scores nearby drivers from Redis GEO search and claims one atomically, and both sides follow the ride live on a map. Services talk over Kafka with retries and dead-letter topics, behind a YARP gateway and SignalR.

• C#
• .NET
• Aspire
• Next.js
• Kafka
• Redis
• PostgreSQL
• SignalR
• Docker Compose

A TinyURL replica: shorten a long address, follow the redirect, and see click analytics by day, hour and referrer. Redis backs a cache-aside store and per-IP rate limiting behind an ASP.NET Core API and a zoneless Angular front end.

• C#
• .NET
• ASP.NET Core
• Angular
• TypeScript
• Redis
• NGINX
• Docker Compose

AI-powered multi-agent travel planner built with LangGraph. Combines live flight data, web search, and LLMs to generate day-by-day itineraries via a FastAPI backend.

• Python
• FastAPI
• Jinja2
• HTML/CSS/JS
• LangGraph
• LangChain
• Groq LLMs
• PostgreSQL
• Tavily API
• AviationStack API

An LLM can solve the hard problem and fail the arithmetic underneath it, and accuracy still scores that as a win. An ETH Zurich paper uses Knowledge Space Theory to test whether a model's right answers respect their prerequisites, and finds knowledge that is fragmented rather than hierarchical.

• AI Engineering
• Gen AI
• LLM Evaluation

A counter in process memory stops meaning anything the moment you run a second replica: each instance enforces its own limit, so ten pods let through ten times the traffic you configured. What it costs to keep one shared count honest.

• System Design
• Distributed Systems

Kafka is not a queue. It is a distributed, append-only commit log that many consumers read at their own pace, and every feature it has follows from that one fact: partitions, consumer groups, offsets, delivery semantics, retention and the outbox trick.

• Backend Engineering
• System Design
• Distributed Systems