Start by picking one programming language and revising the core data structures — arrays, strings, linked lists, stacks, queues, hashmaps, trees, heaps, and graphs — along with key algorithms like binary search, recursion, sorting, greedy techniques, and dynamic programming. A practical DSA interview preparation roadmap is 6–8 weeks of fundamentals with easy problems, 6–8 weeks of pattern-based medium problems, and a final 2–3 weeks of revision plus mock interviews. Maintain a mistake log for every problem you fail and revisit it weekly, because structured revision is what separates selected candidates from random grinding.

DSA interview questions are coding problems that test how well you can apply data structures and algorithms to solve an unfamiliar problem, not just recall definitions. A typical round gives you one or two problems in 45–60 minutes covering topics like arrays, strings, hashing, two pointers, trees, graphs, and dynamic programming. Product-based companies use them to judge your problem-solving approach, code quality, and how you handle edge cases under time pressure.

Start by clarifying the problem — inputs, constraints, and edge cases — then state a brute-force solution before optimising it. Interviewers evaluate your thought process, so think out loud, dry-run your approach on an example, and only then begin coding. End by walking through test cases and stating the time and space complexity. If you get stuck, relate the problem to a known pattern like sliding window, binary search on answer, or BFS/DFS instead of going silent.

Curated problem lists like Striver's SDE Sheet and Love Babbar's DSA Sheet are the most followed in India because they cover the patterns product companies actually ask. Pick one sheet and solve it topic-wise, retrying unsolved problems after a week instead of jumping between multiple sheets. A sheet works best as a checklist on top of conceptual clarity, not as a replacement for it.

Cracking the Coding Interview is the most recommended for understanding interview-style problems, while Elements of Programming Interviews is better for deeper, trickier practice. Most successful candidates pair a book with LeetCode practice and company-wise interview experiences rather than relying on reading alone. Choose one primary book and finish it properly instead of collecting several.

A system design interview is a round where you are asked to design a large-scale system — such as a URL shortener, chat app, or news feed — and defend your architectural choices. You are evaluated on requirement gathering, scalability, database decisions, caching, and trade-offs rather than on writing complete code. It is typically part of hiring for mid-level and senior roles, though many product companies now include system design or LLD rounds for freshers as well.

First learn the building blocks — load balancers, caching, CDNs, SQL vs NoSQL databases, indexing, sharding, message queues, and the CAP theorem. Then study 8–10 classic designs like a URL shortener, rate limiter, and notification system, and practise explaining them on a whiteboard or design tool within 35–40 minutes. Four to six weeks of consistent practice after your DSA preparation is usually enough, and getting feedback from someone who has sat on the interviewer's side speeds it up significantly.

Use a fixed framework: clarify functional and non-functional requirements, do quick back-of-the-envelope estimates, define the API, draw the high-level design, and then deep-dive into components like database schema, caching, and partitioning. Reserve the last few minutes for bottlenecks and trade-offs, because interviewers score you on how you justify decisions, not on a single correct answer. Talking through your reasoning continuously matters as much as the final diagram.

The most frequently asked ones include designing a URL shortener, a chat application like WhatsApp, a news feed like Instagram or Twitter, a ride-sharing service like Uber, a rate limiter, a notification system, and a file storage service like Dropbox. Expect follow-ups on scaling to millions of users, handling failures, and choosing between SQL and NoSQL databases. Practising these end to end covers a large share of what product companies ask.

System Design Interview by Alex Xu is the most widely used — Volume 1 covers load balancing, caching, consistent hashing, and classic designs, while Volume 2 goes into more advanced systems. For deeper fundamentals, Designing Data-Intensive Applications is the standard next step, though it is denser and better after you know the basics. Start with the Alex Xu volumes, then practise designing systems yourself.

Grokking the System Design Interview is a popular online course that breaks down around fifteen classic system design problems using a repeatable template — requirements, estimation, API design, high-level design, and deep dives. It is useful for building a structured approach quickly, especially if you have never faced a design round before. Treat it as a starting framework rather than complete preparation, and follow it up by designing systems on your own.

Start with DSA on LeetCode using one structured sheet, since coding rounds are the first filter at almost every product company. A realistic FAANG interview preparation roadmap is 3–4 months of DSA, followed by 4–6 weeks of system design or LLD depending on your experience level, and the final weeks for behavioural prep and company research. Use GeeksforGeeks for company-specific interview experiences and build referrals through LinkedIn, since off-campus applications in India convert far better with a referral.

They help if you need structure, deadlines, and guided feedback, but self-study with LeetCode, free sheets, and mock interviews works equally well for disciplined candidates. If you do join a FAANG interview preparation course, verify that it includes live mock interviews and covers both DSA and system design rather than only recorded lectures. Most candidates crack these interviews through consistent self-practice combined with a few quality mocks instead of expensive programs.

The coding bar stays high — medium and hard DSA problems are still asked — but system design and behavioural rounds carry far more weight and often decide your final level and compensation. FAANG interview preparation for experienced engineers should therefore focus on deep HLD discussions, defending architectural decisions from past projects, and STAR-format stories around impact, ownership, and conflicts. Two to three months of focused preparation usually works better than a long, drawn-out plan.

Yes, because they recreate the pressure, time limits, and communication demands of a real round, which solo problem-solving cannot replicate. Mocks expose gaps like coding in silence, missing edge cases, or mismanaging the 45 minutes, and the detailed feedback afterwards is what actually drives improvement. Most candidates benefit from two to three mocks in the final weeks before their interviews, ideally with someone who has conducted real interviews at product companies.