About

The engineer behind the work.

Bitan Sarkar, Software Engineer

Kolkata, India

I'm a Software Engineer based in Kolkata, India, currently at Publicis Sapient where I've spent the last 5+ years building and scaling backend systems for Omantel, one of Oman's largest telecom operators, serving over a million subscribers.

My stack centers on Java, Spring WebFlux, and AWS. I've led migrations from IBM WebSphere to cloud-native microservices, built SAML/SSO identity flows from scratch, and managed cross-region DynamoDB migrations under production load. I hold the AWS Solutions Architect – Associate certification.

Outside work, I'm a LeetCode Guardian (450+ problems), actively studying Blockchain and Web3, and writing about system design. I graduated from IIT Bhubaneswar with a BTech in ECE in 2021.

5+

Years at Publicis Sapient

2500+

LeetCode Rating

450+

LeetCode Problems Solved

AWS SAA

Solutions Architect

Journey

Education & Experience

From IIT Bhubaneswar to telecom-scale systems.

  1. 2017

    Joined IIT Bhubaneswar

    B.Tech Electronics & Communication Engineering

    Moved from Salt Lake School, Kolkata to Bhubaneswar to study ECE at IIT BBSR. Joined Coding Society and Chamber of Product, and began competitive programming.

  2. 2018-2021

    Campus Involvement

    Coding Society · Chamber of Product

    Built the IIT BBSR Campus Map Android app. Stayed active in coding competitions through Coding Society and Chamber of Product.

  3. 2021

    Graduated IIT Bhubaneswar

    B.Tech ECE, 2017-2021

    Completed B.Tech in Electronics & Communication Engineering.

  4. 2021

    Joined Publicis Sapient

    Software Development Engineer I

    Started as SDE-I, assigned to the Omantel CXP platform (Telecom, Oman) — later 5+ years of engineering work spanning Java, Spring WebFlux, Kubernetes, and AWS.

  5. 2022

    AWS Certified

    Solutions Architect – Associate

    Earned AWS Solutions Architect Associate certification. Published a widely-read LeetCode Permutations article and a well-received LinkedIn URL shortener design writeup.

  6. 2023-Present

    Omantel CXP Deepdive

    SSO, Spring WebFlux, Kubernetes Infra

    Building SAML/Theqa SSO integration (Login with Theqa v1.5) and debugging SAML SLO issues. Diagnosed Spring WebFlux thread starvation and Hikari pool exhaustion on single-CPU Kubernetes pods. Set up Redis Cluster access via a Node.js proxy through a Windows EC2 jumpbox, runs Gatling load tests, and configures WAF rules. Self-initiated an Ollama-based MR Review Bot, a Config UI, SSM scripts, and a Defect Quality Validator Rovo agent — still ongoing.

  7. 2025-Present

    Systems, Security & Competitive Programming

    eBPF · RAG · CTF · Codeforces Expert

    Building KCPM (Kubernetes process monitor via eBPF/libbpf), a GenericChatBot RAG project, and exploring Blockchain. Designing VulnArena (CTF) and doing bug bounty/ethical hacking research with Burp Suite. Returned to Codeforces after ~8 years and jumped from Pupil (1375) to Expert (1751); reached LeetCode Guardian and authored LC 3669. Now in an active SDE-II/Senior job search targeting product companies.

Toolbox

Skills & Technologies

Color-coded by proficiency: green is expert, amber proficient, blue actively learning.

Languages

JavaPythonGoJavaScriptSQLC

Backend

Spring BootSpring WebFluxNode.jsWebSphere (WAS)GraphQLREST APIs

Cloud

AWS LambdaAWS API GatewayAWS CognitoAWS DynamoDBAWS CloudWatchAWS EventBridgeAWS S3 + CloudFrontAWS EC2AWS SNS

DevOps

TerraformDockerKubernetesArgoCDGitLab CI/CDeBPF / libbpf

Databases

DynamoDBOracle DBMongoDBNeo4jRedis (ElastiCache)

Protocols

SAML / SSOOIDC / OAuth2SOAP

Tools

SonarQubeBrunoOpenVPN

Beyond Code

When I'm not coding…

Competitive Programming

LeetCode Guardian with 450+ problems solved. I keep the algorithmic muscles sharp.

History & Physics

Fascinated by the era of 1850 to 1950: the science, the people, and the ideas that shaped modernity.

Biblical Studies

A long-running personal study: texts, history, and interpretation.

What I Do

Three things I do well

Backend Engineering

Reactive microservices with Spring WebFlux. High-throughput APIs. Authentication systems (SAML, OIDC, Cognito). Built for production scale.

Cloud & AWS

Lambda, API Gateway, DynamoDB, Cognito, EventBridge, CloudWatch, S3, CloudFront. AWS SAA certified. Infrastructure as code with Terraform.

System Design

URL shorteners, auth architectures, serverless pipelines. I document architectural decisions, and my URL shortener article has been widely read on LinkedIn.

Selected Work

Featured Projects

A few things I've built and shipped, from serverless tooling to system-design write-ups.

All projects
Cloud

IRCTC PNR Status Notifier

Serverless PNR status tracker with automatic SMS/email alerts when waitlist clears.

PythonAWS LambdaEventBridgeSNSServerless
Code
DevTools

CloakVPN

Fully automated, GUI-powered VPN system. Terraform provisions OpenVPN EC2s across AWS regions, rotating IPs on demand.

PythonTerraformAWS EC2OpenVPNDevTools
Code
Web Applications

Splitwise Clone

A full-stack expense sharing application with group management and debt simplification algorithms.

Full-StackExpense TrackingWeb DevelopmentAlgorithmsSelf-Hosted
Code
DevTools

Redis Cluster SSM Proxy

Reaches a VPC-locked Redis Cluster through a single SSM port-forwarding tunnel.

Node.jsRedis ClusterElastiCacheAWS SSMNetworking
Code
Backend

Coalesce for Spring Boot

Collapses concurrent calls for the same key into one execution across every pod, not just inside one JVM.

JavaSpring BootWebFluxRedisDistributed Systems
Code

Certification

AWS Solutions Architect – Associate

Designing distributed, resilient and cost-optimized systems on AWS.