From Service to Product:
Your Complete Transition Guide
Tired of support projects at TCS, Infosys, or Wipro? This guide will help you break into product companies where you'll build things that matter.
What's in this guide:
1 Why Make the Switch?
Let's be honest about why you're here. If you're at a service company, you've probably experienced some of these:
Service Company Reality
- ✗ Working on legacy maintenance projects
- ✗ No ownership - just following client specs
- ✗ 3-5% annual hikes (if you're lucky)
- ✗ Outdated tech stacks (Java 6, anyone?)
- ✗ Bench anxiety and utilization pressure
- ✗ Limited learning opportunities
Product Company Reality
- ✓ Build products used by millions
- ✓ Own features end-to-end
- ✓ 20-50% salary jumps (or more)
- ✓ Modern tech stacks and best practices
- ✓ ESOPs with real upside potential
- ✓ Continuous learning culture
The Salary Reality Check
A 3-year experienced developer at TCS earns around ₹5-7 LPA. The same experience at a product company like Razorpay or Swiggy? ₹18-28 LPA. That's not a typo. The gap is real, and it only widens with experience.
2 The Skills Gap (Honest Truth)
Here's what most service company engineers lack - not because you're not smart, but because your job never required these skills:
Data Structures & Algorithms
The #1 barrier. Product companies use DSA to filter candidates. If you can't solve medium LeetCode problems, you won't clear the first round.
System Design
How would you design WhatsApp? Twitter? This is asked for 3+ years experience. Service projects rarely expose you to this level of architecture thinking.
Modern Tech Stack
React, Node.js, Go, Kubernetes, AWS - most service projects don't use these. But the good news? This is the easiest gap to close with self-learning.
Product Thinking
Understanding WHY you're building something, not just HOW. Product companies expect engineers to question requirements and suggest improvements.
3 6-Month Preparation Plan
This is a realistic timeline. Don't believe anyone who says you can do it in 2 weeks. Dedicate 2-3 hours daily, and you'll be ready.
Month 1-2: DSA Foundation
Topics to Cover:
- ✓ Arrays & Strings
- ✓ Hash Maps & Sets
- ✓ Two Pointers & Sliding Window
- ✓ Linked Lists
- ✓ Stacks & Queues
- ✓ Binary Search
Resources:
- • NeetCode 150 (start here)
- • Striver's SDE Sheet
- • LeetCode Easy → Medium
- • Target: 100 problems
Month 3-4: Advanced DSA + Projects
Topics to Cover:
- ✓ Trees & BST
- ✓ Graphs (BFS, DFS)
- ✓ Dynamic Programming
- ✓ Heaps & Priority Queues
- ✓ Backtracking
Side Project:
- • Build 1 full-stack project
- • Use modern stack (React + Node/Go)
- • Deploy on AWS/Vercel
- • Target: 150 more problems
Month 5-6: System Design + Applications
System Design Topics:
- ✓ Scaling basics (Load balancers, CDN)
- ✓ Database design (SQL vs NoSQL)
- ✓ Caching strategies (Redis)
- ✓ Message queues (Kafka)
- ✓ Design URL shortener, Twitter, etc.
Action Items:
- • Update resume (see below)
- • Start applying to companies
- • Practice mock interviews
- • Read "Designing Data-Intensive Applications"
4 Resume Transformation
Your service company resume won't work. Here's how to reframe your experience:
✗ Don't Write This
- "Worked on support and maintenance of Java application for US banking client"
- "Responsible for bug fixing and change requests"
- "Team size: 15, Duration: 2 years"
✓ Write This Instead
- "Optimized database queries reducing API latency by 40% for 10K daily active users"
- "Built automated testing pipeline reducing regression bugs by 60%"
- "Led migration from monolith to microservices, improving deployment frequency 3x"
Resume Must-Haves:
- ✓ Quantifiable impact (%, numbers)
- ✓ Personal projects with GitHub links
- ✓ Modern tech stack mentioned
- ✓ LeetCode/competitive coding profile
- ✓ One-page format (no 3-page resumes)
- ✓ Clean ATS-friendly formatting
5 Interview Preparation
Product company interviews are different. Here's what to expect:
Online Assessment (OA)
2-3 coding problems in 60-90 minutes. Usually on HackerRank or similar.
Technical Round 1 (DSA)
Live coding with an interviewer. They want to see your thought process, not just the solution.
Technical Round 2 (System Design / LLD)
For 3+ years: High-level system design. For juniors: Low-level design (OOP, design patterns).
Hiring Manager / Culture Fit
Behavioral questions using STAR format. They assess if you'll fit the team.
6 Where to Apply
Not all product companies are equally hard to crack. Here's a strategic approach:
Start Here (Easier)
Good for building confidence and getting product experience:
- • Series A-B startups
- • Lesser-known unicorns
- • Companies with urgent hiring
Target These (Medium)
Great balance of brand + opportunity:
- • Swiggy, Meesho, Groww
- • Freshworks, Zoho
- • Urban Company, NoBroker
Dream Companies (Hard)
Apply after 6 months prep or some product experience:
- • Google, Microsoft, Amazon
- • Flipkart, Razorpay, CRED
- • Stripe, Atlassian
Top-Rated Companies Hiring Now:
7 Why Service Engineers Get Rejected (And How to Avoid It)
After reviewing hundreds of failed interviews, these are the most common reasons service company engineers don't make the cut:
Resume Red Flags
What Gets You Rejected:
- ✗ "Worked on client project for XYZ Bank" (screams service company)
- ✗ No metrics or impact mentioned
- ✗ 3-page resume with irrelevant details
- ✗ Only listing technologies, not achievements
- ✗ No GitHub/portfolio links
What Gets You Shortlisted:
- ✓ "Reduced API latency by 40%" (specific impact)
- ✓ Side projects with live demos
- ✓ Clean one-page format
- ✓ Open source contributions
- ✓ LeetCode/competitive coding profile
DSA Interview Failures
Mistake #1: Jumping to Code
Service engineers often start coding immediately without understanding the problem. Interviewers want to see your thought process.
✓ Fix: Spend 5-10 minutes clarifying requirements, discussing examples, and explaining your approach before writing code.
Mistake #2: Silent Coding
Coding in silence makes it impossible for interviewers to evaluate you. They can't read your mind.
✓ Fix: Think aloud. Explain what you're doing and why. "I'm using a hashmap here because we need O(1) lookup..."
Mistake #3: Giving Up Too Early
Saying "I don't know" after 2 minutes. Interviewers want to see how you handle challenges.
✓ Fix: Break down the problem. Ask for hints if stuck. Show your problem-solving process even if you don't get the optimal solution.
Mistake #4: Not Testing Your Code
Submitting code without dry-running it through examples. Shows lack of attention to detail.
✓ Fix: Always trace through your code with the given examples. Check edge cases (empty input, single element, duplicates).
System Design Failures (3+ YOE)
Mistake #1: Not Asking Clarifying Questions
"Design Twitter" is intentionally vague. Jumping straight to architecture without understanding scale and requirements is a red flag.
✓ Fix: Ask about DAU, read/write ratio, latency requirements, geographic distribution. Spend 5 minutes on requirements.
Mistake #2: Over-Engineering from Start
Adding Kubernetes, microservices, and Kafka before explaining the basic flow. Shows you're pattern-matching, not thinking.
✓ Fix: Start simple. Design for 1000 users first, then explain how you'd scale to 1 million.
Mistake #3: Ignoring Trade-offs
Every design decision has trade-offs. Not discussing them shows shallow understanding.
✓ Fix: For every choice, explain the trade-off. "I'm choosing SQL over NoSQL because we need ACID transactions, but we'll lose some write throughput."
Behavioral Interview Mistakes
Don't Do This:
- • Badmouthing your current employer ("TCS is terrible")
- • Taking credit for team work ("I built the entire system")
- • Vague answers without specific examples
- • Saying you have no weaknesses
- • Showing desperation ("I'll take any role")
Do This Instead:
- • Focus on growth ("I want more ownership")
- • Use "we" for team, "I" for your contribution
- • Use STAR format (Situation, Task, Action, Result)
- • Show self-awareness with genuine growth areas
- • Show specific interest in the company
Surface-Level Technical Knowledge
Product companies dig deep. Saying "I know Spring Boot" isn't enough. They'll ask HOW it works internally.
Questions That Expose Surface Knowledge:
- • "How does HashMap work internally? What happens during collision?"
- • "Explain the difference between processes and threads at the OS level"
- • "How does HTTPS handshake work?"
- • "What happens when you type a URL in browser?" (The classic)
- • "How does garbage collection work in Java/Go?"
✓ Fix: Don't just learn to USE technologies. Understand HOW they work. Read documentation, not just tutorials.
8 Week-by-Week DSA Roadmap (24 Weeks)
This is the exact roadmap that works. Follow it religiously for 6 months, 2-3 hours daily.
Target: Solve 250-300 problems total. Focus on patterns, not memorization. After each topic, you should be able to recognize which pattern applies to a new problem.
Phase 1: Foundation (Weeks 1-8)
Weeks 1-2: Arrays & Hashing
Concepts:
- • Array traversal, manipulation
- • HashMap/HashSet usage
- • Frequency counting
- • Prefix sums
Must-Solve Problems:
- • Two Sum
- • Contains Duplicate
- • Valid Anagram
- • Group Anagrams
- • Top K Frequent Elements
- • Product of Array Except Self
Target: 25 problems
Weeks 3-4: Two Pointers & Sliding Window
Concepts:
- • Two pointer technique
- • Fast & slow pointers
- • Fixed & variable window
- • Shrinking window pattern
Must-Solve Problems:
- • Valid Palindrome
- • 3Sum
- • Container With Most Water
- • Best Time to Buy and Sell Stock
- • Longest Substring Without Repeating
- • Minimum Window Substring
Target: 25 problems
Weeks 5-6: Binary Search
Concepts:
- • Basic binary search
- • Search in rotated array
- • Binary search on answer
- • Lower/upper bound
Must-Solve Problems:
- • Binary Search
- • Search in Rotated Sorted Array
- • Find Minimum in Rotated Array
- • Search a 2D Matrix
- • Koko Eating Bananas
- • Median of Two Sorted Arrays
Target: 20 problems
Weeks 7-8: Linked Lists & Stacks
Concepts:
- • Linked list traversal & manipulation
- • Fast & slow pointer (cycle detection)
- • Stack for parentheses, monotonic stack
- • Queue implementations
Must-Solve Problems:
- • Reverse Linked List
- • Merge Two Sorted Lists
- • Linked List Cycle
- • LRU Cache
- • Valid Parentheses
- • Daily Temperatures
Target: 25 problems
Phase 2: Intermediate (Weeks 9-16)
Weeks 9-10: Trees (Binary Trees & BST)
Concepts:
- • Tree traversals (inorder, preorder, postorder)
- • Level order traversal (BFS)
- • BST properties & operations
- • Tree construction from traversals
Must-Solve Problems:
- • Invert Binary Tree
- • Maximum Depth of Binary Tree
- • Same Tree
- • Binary Tree Level Order Traversal
- • Validate BST
- • Lowest Common Ancestor
Target: 25 problems
Weeks 11-12: Trees (Advanced) & Tries
Concepts:
- • Tree DP (path problems)
- • Serialize/deserialize trees
- • Trie data structure
- • Prefix matching
Must-Solve Problems:
- • Binary Tree Maximum Path Sum
- • Serialize and Deserialize Binary Tree
- • Implement Trie
- • Word Search II
- • Design Add and Search Words
Target: 20 problems
Weeks 13-14: Graphs (BFS & DFS)
Concepts:
- • Graph representations (adjacency list/matrix)
- • BFS for shortest path (unweighted)
- • DFS for connectivity, cycles
- • Grid-based graph problems
Must-Solve Problems:
- • Number of Islands
- • Clone Graph
- • Course Schedule (cycle detection)
- • Pacific Atlantic Water Flow
- • Rotting Oranges
- • Word Ladder
Target: 25 problems
Weeks 15-16: Graphs (Advanced) & Heaps
Concepts:
- • Topological sort
- • Union-Find (Disjoint Set)
- • Dijkstra's algorithm basics
- • Heap/Priority Queue
Must-Solve Problems:
- • Course Schedule II
- • Number of Connected Components
- • Redundant Connection
- • Kth Largest Element
- • Merge K Sorted Lists
- • Find Median from Data Stream
Target: 25 problems
Phase 3: Advanced (Weeks 17-24)
Weeks 17-18: Dynamic Programming (1D)
Concepts:
- • Identifying DP problems
- • Memoization vs tabulation
- • State definition & transitions
- • 1D DP patterns
Must-Solve Problems:
- • Climbing Stairs
- • House Robber I & II
- • Coin Change
- • Longest Increasing Subsequence
- • Word Break
- • Decode Ways
Target: 25 problems
Weeks 19-20: Dynamic Programming (2D)
Concepts:
- • 2D grid DP
- • String DP (LCS, Edit Distance)
- • Interval DP
- • State compression (if time permits)
Must-Solve Problems:
- • Unique Paths
- • Longest Common Subsequence
- • Edit Distance
- • 0/1 Knapsack
- • Target Sum
- • Longest Palindromic Substring
Target: 25 problems
Weeks 21-22: Backtracking & Intervals
Concepts:
- • Backtracking template
- • Permutations & combinations
- • Interval problems
- • Greedy algorithms
Must-Solve Problems:
- • Subsets I & II
- • Permutations
- • Combination Sum
- • N-Queens
- • Merge Intervals
- • Meeting Rooms II
Target: 25 problems
Weeks 23-24: Revision & Mock Interviews
Focus Areas:
- • Revise weak topics
- • Timed LeetCode contests
- • Mock interviews (Pramp, Interviewing.io)
- • Company-specific problem sets
Action Items:
- • Do 3-4 mock interviews
- • Solve company-tagged problems
- • Review all notes
- • Practice explaining solutions aloud
Target: Revision + 20 new problems
Pro Tips for DSA Preparation:
- ✓ Don't just solve, understand patterns. After each topic, you should recognize which pattern applies to new problems.
- ✓ Revise solved problems. Re-solve problems you did 2 weeks ago. Spaced repetition works.
- ✓ Time yourself. In interviews, you get 30-45 minutes per problem. Practice under time pressure.
- ✓ Write clean code. Variable names, proper indentation. Interviewers notice this.
9 Recommended Resources
The best resources we recommend for cracking product company interviews. Links with * are affiliate links - you pay the same price, and we earn a small commission to keep this site running.
💻 DSA Practice Platforms
LeetCode Premium *
Company-specific questions, solution videos, and premium problems. Essential for serious prep.
NeetCode Pro *
Excellent video explanations with pattern-based learning. Great for visual learners.
AlgoExpert *
170 hand-picked problems with detailed video explanations. Good for structured prep.
🏗️ System Design
Grokking System Design (Educative) *
The most popular system design course. Interactive with real interview questions.
System Design Interview (Alex Xu) *
The bible of system design interviews. Both volumes are must-reads.
ByteByteGo *
Visual system design explanations from Alex Xu. Great newsletter + course.
🎯 Behavioral & Soft Skills
🆓 Best Free Resources
Our recommendation: Start with free resources (NeetCode YouTube, Striver). If you're serious about prep and can afford it, LeetCode Premium + one system design resource (Educative or Alex Xu's book) is the winning combo.
10 Frequently Asked Questions
Real questions from engineers making the switch, answered honestly.
Ready to Make the Switch?
The best time to start was yesterday. The second best time is now. Your future self will thank you.