Paytm SDE-1 Interview Experience (2024–25)
A step-by-step prep guide from CodeKerdos mentors & learners who got offers
Over the last hiring cycles, multiple CodeKerdos learners cleared Paytm for SDE-1. This blog distills exactly what they faced, plus corroborating public reports, so you can prep with evidence, not guesswork.
TL;DR (Quick Snapshot)
Rounds: Typically 3–5: Online Assessment → 1–2 Technical DSA rounds → (team-dependent) LLD → Hiring Manager/HR.
OA: Frequently on HackerRank (some off-campus OAs on CoCubes). Expect 2–4 DSA problems + a few CS/Java/SQL MCQs.
Tech rounds: Live coding, often in a shared doc/Google Docs, with medium-level DSA and follow-ups on complexity and tests.
LLD (if asked): Classic prompt seen repeatedly—“Design a Hotel/Hotel-Booking System.
Round 1: Online Assessment (HackerRank / CoCubes)
Round 2: Technical DSA (Live Coding)
Round 3: Low-Level Design (team-dependent)
Round 4: Hiring Manager / HR
What to Prepare (Topic-by-topic)
Real Questions & Patterns
CodeKerdos Mentor Tips
Round 1: Online Assessment
Duration: 60–90 minutes
Format (most common): 2–4 DSA problems + ~5–10 MCQs (Java/SQL/DSA basics)
Platform: Often HackerRank; some off-campus drives used CoCubes (3 coding problems / 70 min).
Topics that show up a lot
Arrays & Strings: sliding window, two-pointers, prefix/suffix sums
Hashing & Heaps: frequency, top-K, de-duplication
Graphs: BFS/shortest-path on grids, topo-style ordering
DP: subset/knapsack flavor, LIS/variations
MCQs: SQL joins/indexing, OOP/collections, basic OS/DB concepts
Our Mentor’s Tip:
“The OA isn’t just about AC. Reviewers like candidates who explain edge cases, prove complexity, and write clean, modular code. If there’s time, add a tiny test harness to demonstrate cases.”
Round 2: Technical DSA (Live Coding)
Count: Usually 1–2 rounds
How it runs:
Quick intro → 1–2 medium DSA problems
Code in a shared doc/Google Docs or a simple editor
Walk through test cases and Big-O; discuss alternative approaches
Question flavors our learners met (and you’ll see publicly)
Trees: Top View / Right View, level-order variants, LCA
Strings & Hashing: anagram grouping, sliding-window uniques
Graphs: BFS/shortest path, islands
DP: array/sequence DP
Public reports explicitly mention “coding on Google Docs” and “top view of a binary tree” asked in Paytm loops.
CodeKerdos Mentor Tip (Live DSA):
“Narrate a mini-plan before coding:
Input → constraints → examples → brute → optimal → complexity → test.
This 60-second structure buys trust and reduces rework.”
Round 3: Low-Level Design (LLD) — team-dependent
Not every SDE-1 loop has LLD, but many backend-leaning teams do.
Common prompt:
Design a Hotel / Hotel-Booking System → entities, reservations, availability search, cancellation/refunds, prevention of double-booking, persistence and indexes, sequence diagram for booking/cancel flows, and basic failure handling (idempotency + retries). Glassdoor+1
How to frame your answer (what we coach):
Scope & assumptions (actors, QPS, latency, data size)
Core entities (Hotel, Room, Inventory, Reservation, Payment)
APIs & flows (search → hold → confirm → cancel)
State & storage (tables, keys, indexes)
Correctness (transactions, idempotency, double-booking prevention)
Reliability (retries/backoff, DLQ, observability)
Scale knobs (caching, sharding, rate limits)
Our Mentor’s Tip (LLD):
“Interviewers reward clarity and safety. Keep the model small, call out idempotency, and narrate the failure path before you optimize.”
Round 4: Hiring Manager / HR
Focus areas:
Ownership stories (incidents, spikes during sales/festivals, deadlines)
Communication with cross-functional teams (QA, Ops, Data, Risk)
Measurable impact (P95/P99 latency, throughput, error rate, cost)
Product sense and prioritization (build vs buy, ‘what would you ship first and why?’)
Learner Note (placed at Paytm):
“My HM round was 70% project deep-dive. I led with metrics (before/after) and a short ‘what I’d do next’ roadmap.”
What to Prepare (Company-specific emphasis)
DSA Core: arrays/strings, sliding window, hashing, trees/graphs; be fluent with proof of complexity and counter-examples. (Matches repeated Paytm reports.)
SQL & CS MCQs for OA: joins, indexes, isolation basics; Java collections/OOP. (Frequently reported in Paytm OAs.)
LLD (if backend): practice Hotel/Booking plus one fintech-y mock (Wallet/Ledger) to get used to idempotency and retries.