karthikeyan.rajendran
/ home

Backend-focused fullstack developer for distributed systems, identity & cloud-native infrastructure.

7 years building and operating microservices, event-driven pipelines, and identity & access management systems. Based in Berlin — open to full-time roles and freelance engagements.

status
available
experience
7 yrs
location
berlin, de
timezone
cet (utc+1)
/profile

About

Karthikeyan Rajendran

I've spent 7 years designing, building, and operating backend systems — from event-driven microservices processing 100,000+ Kafka messages a day in a regulated fintech environment, to a self-deployed production identity platform I built, ran, and later migrated between auth providers based on real production trade-offs. Recently I extended that identity & access management focus into federated protocols — standing up a real Shibboleth-IdP, LDAP, and SAML 2.0 trust chain from scratch, the kind of infrastructure German university systems run in production.

Before software, I ran my own hospitality business — end-to-end ownership, client relationships, and operations. That instinct for owning outcomes, not just tickets, carried straight into engineering.

/projects/physical-ai-safety

Physical AI warehouse safety platform

A real-time safety monitoring platform for logistics facilities: edge cameras run YOLO/ByteTrack detection locally, an Azure Flink pipeline classifies near-misses and zone violations in real time, and a Three.js digital twin renders live asset positions and danger zones. Faces are anonymized at the edge before any data leaves the site — GDPR-by-design.

Multi-tenant PostgreSQL with row-level security, Keycloak (OAuth 2.0/OIDC) for auth, and a config studio that pushes JSON configs straight to edge units for enforcement — the identity, data-isolation, and event-pipeline concerns sit directly in my backend/IAM focus area.

Note: the live link below is a mocked front-end demo showcasing the UI and architecture — not a deployed production system like job-tracker.in.

Azure Apache Flink FastAPI PostgreSQL RLS Keycloak Three.js Docker
/projects/job-tracker

job-tracker.in

A production job-application tracker, owned end to end

Architected and shipped a REST API with a 5-stage workflow, pagination, sorting, and dynamic filtering — from design to live cloud deployment. Includes a Chrome extension that auto-fills applications from LinkedIn directly into the tracker.

Implemented identity management with Keycloak (OAuth 2.0 / OIDC / JWT / RBAC) in production, then made the call to migrate to Supabase Auth after weighing operational trade-offs between self-hosted and managed identity — a decision made from running both, not from a tutorial.
Java 21 Spring Boot 3 PostgreSQL Docker GitHub Actions React 18 TypeScript
/projects/federated-iam

Federated identity POC — Shibboleth-IdP, LDAP & SAML 2.0

Built a real, working federation from scratch: an LDAP directory running the eduPerson schema, a genuine Shibboleth-IdP instance issuing signed SAML assertions, and a Spring Boot Service Provider verifying them end to end — the same architecture German university identity federations (DFN-AAI) run in production.

  • Loaded the real eduPerson schema live into a running LDAP server
  • Diagnosed a three-layer keystore failure chain — missing file, wrong password, OpenSSL/JVM PKCS12 incompatibility
  • Traced an undocumented Spring Boot 4 breaking change (SAML2 autoconfig split into its own starter) by reading the actual classpath, not outdated docs
  • Fully containerized with Docker Compose across three services
Shibboleth-IdP OpenLDAP SAML 2.0 Spring Security 7 Docker Compose
/projects/schichtplanung

Schichtplanung — shift planning for warehouse & logistics teams

A shift-scheduling application for logistics operations, with authenticated login and a management dashboard for organizing and coordinating employee shifts across a warehouse team.

Auth Dashboard Logistics
/experience

Experience

Software Developer 09.2022 – 01.2026
Cognizant Technology — Client: Altares Dun & Bradstreet

Led 10+ production microservices for 100,000+ enterprise users; built Kafka pipelines processing 100,000+ messages/day at 99.9% uptime; delivered enterprise SSO and X.509 certificate authentication over SOAP APIs.

Senior Software Engineer 04.2021 – 08.2022
Prodapt Solutions — Client: Lumen Technology

Designed real-time network telemetry microservices; cut fault-analysis query time ~40% via Neo4j graph modelling.

Software Engineer 04.2019 – 04.2021
Tech Mahindra — Client: AT&T

Built Apache Camel integration services with TDD discipline; 85%+ test coverage, ~30% fewer production incidents.

/skills

Skills

Backend & Architecture
Java 17/21Spring Boot 3 MicroservicesHexagonal / DDD Event-Driven Systems
Identity & Security
OAuth 2.0 / OIDCSAML 2.0 KeycloakAuth0 Azure ADX.509
Data & Messaging
KafkaPostgreSQL MongoDBNeo4jRedis
Cloud & DevOps
DockerKubernetes LinuxGitHub Actions AWSDigitalOcean
/engage

Let's talk

Open to full-time backend/IAM roles and scoped freelance engagements.

Hiring for a role?

Backend-focused fullstack developer with production IAM, Kafka, and cloud-native experience — immediately available, based in Berlin.

Email me →

Have a project?

  • Backend API development (Spring Boot)
  • OAuth2 / SAML / IAM integration
  • Kafka & event-driven pipelines
  • Legacy → microservices migration
  • Docker / CI-CD setup for small teams
Start a project →