Parv Khandelwal
I'm a freelance Java backend developer building scalable, event-driven microservices for startups and product teams.
I help teams ship high-concurrency systems with 
High-Concurrency Flash Sale System
Stateless JWT auth eliminating per-request DB roundtrips, decoupled checkout via a Kafka order queue, and an atomic Token Bucket rate-limiter in Redis using Lua scripting. Cut DB load by 40%.
Java 21Spring BootKafkaRedis
PostgreSQL
Prometheus
DockerReal-Time Fraud Detection Pipeline
Kafka-backed engine processing 500+ TPS at sub-100ms latency, Hibernate optimistic locking, and live alerts via WebSockets in under 200ms.
Spring Boot
Python MLKafkaDockerTicket Reservation Engine
Distributed seat reservation backend handling 500 concurrent users with zero double-bookings. Redis distributed locks as the first line of defense, PostgreSQL pessimistic locking (SELECT FOR UPDATE) as the vault, and Kafka Transactional Outbox Pattern to prevent dual-write failures. Background sweeper eliminates zombie locks after Redis crashes.
Java 21Spring BootRedisPostgreSQLApache KafkaDocker
TestcontainersLead Management System — CRM
A production-ready webhook-based CRM that automatically captures leads from contact forms into a unified dashboard. Built for a digital marketing agency in Alwar.
Spring BootNeon Postgres
Render
Vercel
JWT- Event-driven microservices with Kafka
- REST APIs with Spring Boot & JPA
- Redis caching & rate limiting
- Observability with Prometheus/Grafana
- Dockerised deployments & CI/CD
