Fahim Ul Haq

When an interviewer asks you to design an e-commerce system, they are not asking you to build a website with product pages and a checkout button. They are testing whether

When you begin learning System Design, you quickly realize that scalability is not just about adding more servers. It is about understanding how a single machine behaves under pressure before

Most engineers feel overwhelmed when preparing for System Design interviews, partly because System Design seems limitless, and partly because interviewers expect clarity under extreme time constraints.  The good news is

Designing Zoom is a popular System Design interview problem because it forces candidates to reason about real-time communication under strict performance constraints. Unlike text-based systems, video conferencing introduces challenges around

When interviewers ask you to design a distributed logging system, they are not testing whether you know the internals of Elasticsearch or can recite the Kafka API. They are testing

Designing Slack is a popular System Design interview problem because it tests a candidate’s ability to reason about real-time systems at scale. Unlike simpler CRUD-based applications, Slack introduces challenges such

When you are asked to design Google Calendar, interviewers are not testing whether you can store events in a database. They are testing whether you can reason about time, collaboration,

When you are asked to design Pastebin in a System Design interview, the interviewer is not testing whether you understand Pastebin as a product. They are testing whether you can

A strong architecture is not a giant diagram. It is a set of deliberate choices: what to build first, what to postpone, what to standardize, and what risks you’re willing

Security-focused rounds are rarely about listing OWASP items. They are about showing that you can reason from threats to controls, draw explicit trust boundaries, and build systems that stay safe