A system design interview tests your ability to architect a large-scale software system, usually through open-ended prompts like "Design a URL shortener" or "Design Instagram." There is no single correct answer — you are evaluated on how you gather requirements, handle scale (users, data, traffic), choose components such as databases, caches and load balancers, and justify trade-offs. Product-based companies in India commonly run two formats: High-Level Design (HLD) for overall architecture and Low-Level Design (LLD) for class-level, object-oriented design.

Build fundamentals first — load balancing, caching, SQL vs NoSQL databases, sharding, message queues, CDNs and consistency trade-offs — then study 10–15 classic designs such as URL shorteners, chat apps and news feeds. Follow a structured book or course so your learning is sequential, and rehearse each design out loud within a 40–45 minute window, just like the real interview. In the final weeks, take system design mock interviews for honest feedback — mentors from product companies, such as Avinash Kumar (SDE-3 at Walmart, 5,000+ students mentored), conduct dedicated HLD and LLD mock interviews that mirror the actual format.

Use a clear framework: (1) clarify functional and non-functional requirements instead of assuming them; (2) do quick back-of-the-envelope estimates for users, storage and traffic; (3) define the core APIs; (4) draw a high-level diagram covering clients, servers, database, cache and queues; (5) deep-dive into one or two critical components such as the data model, caching strategy or sharding; (6) finish by discussing bottlenecks and trade-offs. Keep talking throughout — interviewers score your reasoning and communication as much as the final design.

Grokking the System Design Interview is a widely used online course that teaches HLD through classic case studies — URL shortener, WhatsApp, Netflix-style streaming and similar systems — broken into repeatable steps. It is a solid starting point if you are new to system design because it builds vocabulary and a mental template quickly. The honest answer to "is Grokking the System Design Interview worth it" is: yes for fundamentals, no as your only preparation. You still need to design systems from scratch, defend your choices out loud, and get feedback — which is where peers and mock interviews matter most.

The most frequently asked system design interview questions include designing a URL shortener, a chat app like WhatsApp, an Instagram-style news feed, a video platform like YouTube, a ride-hailing app like Uber or Ola, a food delivery app like Swiggy or Zomato, a rate limiter, a notification system, and a ticket-booking system like BookMyShow. For LLD rounds, expect parking lot, Splitwise and elevator-style problems. Instead of skimming dozens of prompts, master 10–12 of these deeply — most product company interviews are variations of the same core patterns.

For most candidates, the System Design Interview by Alex Xu is the right starting book — Volume 1 and Volume 2 explain each design step by step with diagrams, which makes HLD approachable even for freshers. After that, Designing Data-Intensive Applications is the standard next step for deeper understanding of databases, replication and consistency, especially for SDE-2 and above rounds. Remember that no system design interview book replaces practice — pair your reading with designing systems on a whiteboard and discussing them aloud.

Give yourself 3–6 months of consistent practice. Pick one language (Java, C++ or Python) and stick to it, learn the core data structures — arrays, strings, hashing, linked lists, stacks, queues, trees, graphs and heaps — and then patterns like two pointers, sliding window, binary search, recursion and dynamic programming. Move from topic-wise problems to mixed sets to simulate real interviews, maintain an error log of mistakes, and revise patterns weekly. Around 300–500 well-understood problems beat 1,000 random ones, and a DSA mock interview near the end helps you handle time pressure.

Follow a structured method: repeat the question and confirm constraints, work through an example including edge cases, state a brute-force approach with its complexity, and then optimize by identifying the underlying pattern before writing code. While coding, narrate your thought process, use clean variable names, and dry-run your solution against test cases at the end. Interviewers at product companies evaluate how you think and communicate under pressure, not just whether the final code runs — so practising out loud is as important as solving more problems.

Freshers are most commonly tested on arrays and strings (two pointers, sliding window), hashing, linked lists, stacks and queues, binary search, tree traversals, BFS and DFS on graphs, recursion, and introductory dynamic programming — these dominate the online assessments and interview rounds of product-based companies hiring in India. Instead of memorising DSA interview questions and answers, focus on recognising which pattern each problem maps to, because that is what actually decides whether you clear the round. If you want a curated set rather than hunting across platforms, mentors such as Avinash Kumar (SDE-3 at Walmart, 5,000+ students mentored) share FAANG and product-based company problem lists through their guidance sessions.

iOS development is the process of building applications for Apple devices — iPhone and iPad — mainly using the Swift language with SwiftUI or UIKit inside Xcode. In India, iOS developers are hired by product companies, Global Capability Centres, fintech firms and consumer startups, and the talent pool is noticeably smaller than for Android, which often means less competition for skilled candidates. The day-to-day work covers UI building, API integration, local storage, performance tuning and App Store release cycles.

Follow a staged iOS development roadmap: start with Swift fundamentals, then learn Xcode and build your first simple app with SwiftUI; next cover networking (REST APIs, JSON), local storage (UserDefaults, Core Data), version control with Git, and concurrency (async/await, GCD). Build and publish 2–3 portfolio apps on the App Store or TestFlight, since shipped apps carry far more weight than certificates in interviews. Apple's free official tutorials and Stanford's CS193p course are reliable starting resources, and once your fundamentals are in place, an iOS mock interview with an experienced iOS developer is the fastest way to find your gaps before the real thing.

With 2–3 focused hours a day, a complete beginner usually needs 6–9 months to become job-ready with a small portfolio, while someone who already knows programming or DSA can get there in 3–5 months. Building genuine depth — UIKit, app architecture, performance and mobile system design — typically takes another 1–2 years of real project work. Students targeting iOS roles during placements should ideally start by their second or third year of college.

For most people who enjoy mobile and product building, yes. India has a large base of premium iPhone users, and product companies, GCCs and consumer startups keep hiring for iOS roles; because far fewer developers specialise in iOS compared to Android, skilled candidates often face less competition and stronger salary negotiations. The trade-offs are real, though — you need a Mac to build properly, tools like SwiftUI evolve quickly, and most roles are concentrated in hubs like Bengaluru, Hyderabad, Pune and the NCR. If those conditions suit you, iOS development is a strong, future-proof specialisation.

Xcode, the official iOS development tool, runs only on macOS, so you cannot build and run iOS apps directly on a Windows PC. Your practical options are: use a Mac (even an entry-level Mac mini is enough), rent a cloud Mac service such as MacStadium or MacInCloud, or start by learning Swift on Windows using the open-source Swift toolchain and online playgrounds. Cross-platform frameworks like Flutter and React Native still require a Mac to compile the final iOS build. A sensible path for students is to master Swift and DSA on any machine first, then invest in a Mac once you start building real apps.

Learn Swift first — it has been Apple's primary iOS development language since 2014, and virtually all new iOS roles, tutorials and libraries assume it. Pair it with SwiftUI for building modern interfaces, and pick up UIKit gradually since many existing apps still use it. Objective-C is only worth learning later, if you join a team maintaining a legacy codebase — starting with it today would only slow you down.